[BLU R1 HD Guides, News, & Discussion] bibikalka:
First of all, DO not take any OTA !!! This will update a lot of stuff, and will potentially compromise the rootable holes.

Some debug :

tested (no Root) :

fastboot oem append-cmdline "androidboot.unlocked_kernel=true"
fastboot continue

build.prop

# begin build properties
# autogenerated by buildinfo.sh
ro.build.id=MRA58K
ro.build.display.id=alps-mp-m0.mp1-V2.39.1_blu6735.35gu.m0_P63
ro.build.version.incremental=1466146428
ro.tcustom.build.version=BLU_R0010UU_V6.1_GENERIC
ro.custom.build.version=BLU_R0010UU_V6.1_GENERIC 17-06-2016 14:53
ro.internal.build.version=P6607BN_6.0_BLU_AMZ_US_33
ro.build.version.sdk=23
ro.build.version.codename=REL
ro.build.version.all_codenames=REL
ro.build.version.release=6.0
ro.build.version.security_patch=2016-06-01
ro.build.version.base_os=
ro.build.date=Fri Jun 17 14:56:24 CST 2016
ro.build.date.utc=1466146584
ro.build.type=user
ro.build.user=android
ro.build.host=ubuntu
ro.build.tags=release-keys
ro.build.flavor=full_p6601-user
ro.product.model=R1 HD
ro.product.brand=BLU
ro.product.name=R1_HD
ro.product.device=R1_HD
ro.product.board=R1_HD
ro.custom.build.version.part=BLU_R0010UU_V6.1_GENERIC
ro.fota.version.display=BLU_R0010UU_V6.1_GENERIC 17-06-2016 14:53
# ro.product.cpu.abi and ro.product.cpu.abi2 are obsolete,
# use ro.product.cpu.abilist instead.
ro.product.cpu.abi=armeabi-v7a
ro.product.cpu.abi2=armeabi
ro.product.cpu.abilist=armeabi-v7a,armeabi
ro.product.cpu.abilist32=armeabi-v7a,armeabi
ro.product.cpu.abilist64=
ro.product.manufacturer=BLU
ro.wifi.channels=
ro.board.platform=mt6735
# ro.build.product is obsolete; use ro.product.device
ro.build.product=R1_HD
# Do not try to parse description, fingerprint, or thumbprint
ro.build.description=full_p6601-user 6.0 MRA58K 1466146428 release-keys
ro.build.fingerprint=BLU/R1_HD/R1_HD:6.0/MRA58K/1466146428:user/release-keys
ro.build.characteristics=default
# end build properties
#
# from /home/android/.jenkins/jobs/P6607_6.0_BLU_US_AMZ_TSDS/workspace/baseline/vendor/tinno/p6601/blu_us/system.prop
#
#
# system.prop for generic sdk
#

rild.libpath=mtk-ril.so
rild.libargs=-d /dev/ttyC0

# MTK, Infinity, 20090720 {
wifi.interface=wlan0
# MTK, Infinity, 20090720 }

# MTK, mtk03034, 20101210 {
ro.mediatek.wlan.wsc=1
# MTK, mtk03034 20101210}
# MTK, mtk03034, 20110318 {
ro.mediatek.wlan.p2p=1
# MTK, mtk03034 20110318}

# MTK, mtk03034, 20101213 {
mediatek.wlan.ctia=0
# MTK, mtk03034 20101213}

#
wifi.tethering.interface=ap0
#

ro.opengles.version=196608
#ro.kernel.qemu=1
#ro.kernel.qemu.gles=0

wifi.direct.interface=p2p0
dalvik.vm.heapgrowthlimit=128m
dalvik.vm.heapsize=256m

# USB MTP WHQL
ro.sys.usb.mtp.whql.enable=0

# Power off opt in IPO
sys.ipo.pwrdncap=2

ro.sys.usb.storage.type=mtp,mass_storage

# USB BICR function
ro.sys.usb.bicr=yes

# USB Charge only function
ro.sys.usb.charging.only=yes

# audio
ro.camera.sound.forced=0
ro.audio.silent=0

ro.zygote.preload.enable=0

# temporary enables NAV bar (soft keys)
qemu.hw.mainkeys=0

ro.kernel.zio=38,108,105,16
#ro.kernel.qemu=1
#ro.kernel.qemu.gles=0
#ro.boot.selinux=disable

# Disable dirty region for Mali
debug.hwui.render_dirty_regions=false

ro.sf.lcd_density=320

# performance
ro.mtk_perf_simple_start_win=1
ro.mtk_perf_response_time=1

#
# ADDITIONAL_BUILD_PROPERTIES
#
ro.carrier=unknown
ro.usb.mtp.default=true
ro.blu.product=R1_HD_R0010UU_GENERIC
persist.sys.timezone=America/Los_Angeles
ro.com.android.dateformat=EE-MMM-d-yyyy
ro.config.ringtone=BLU_Ringtone4.mp3
ro.config.notification_sound=BLU_Message3.mp3
ro.config.alarm_alert=alarmclock2.mp3
ro.operator.optr=CUST
ro.setupwizard.suppress_d2d=true
ro.setupwizard.suppress_d2d_nfc=true
ro.myos.version=3.0.0.r325
ro.myos.releasetime=2016.06.17
ro.project.pcb.version=P6607BN_MB_6L_1_HDI_V1.2
dalvik.vm.heapgrowthlimit=128m
dalvik.vm.heapsize=256m
ro.mediatek.chip_ver=S01
ro.mediatek.version.release=alps-mp-m0.mp1-V2.39.1_blu6735.35gu.m0_P63
ro.mediatek.platform=MT6735
ro.telephony.sim.count=2
persist.radio.default.sim=0
persist.radio.multisim.config=dsds
persist.gemini.sim_num=2
ro.gemini.smart_sim_switch=false
ril.specific.sm_cause=0
bgw.current3gband=0
ril.external.md=0
ro.mtk_cam_lomo_support=1
ro.sf.hwrotation=0
curlockscreen=0
ro.mediatek.gemini_support=true
persist.radio.fd.counter=15
persist.radio.fd.off.counter=5
persist.radio.fd.r8.counter=15
persist.radio.fd.off.r8.counter=5
drm.service.enabled=true
fmradio.driver.enable=1
ril.first.md=1
ril.flightmode.poweroffMD=1
ril.telephony.mode=0
dalvik.vm.mtk-stack-trace-file=/data/anr/mtk_traces.txt
mediatek.wlan.chip=CONSYS_MT6735
mediatek.wlan.module.postfix=_consys_mt6735
ril.read.imsi=1
ril.radiooff.poweroffMD=0
ro.frp.pst=/dev/block/platform/mtk-msdc.0/11230000.msdc0/by-name/frp
ro.sys.usb.storage.type=mtp,mass_storage
ro.mediatek.version.branch=alps-mp-m0.mp1
ro.mediatek.version.sdk=4
ro.setupwizard.mode=OPTIONAL
ro.com.google.gmsversion=6.0_r4
ro.com.google.clientidbase=android-blu
ro.com.google.clientidbase.ms=android-blu
ro.com.google.clientidbase.yt=android-blu
ro.com.google.clientidbase.am=android-blu
ro.com.google.clientidbase.gmm=android-blu
ro.mtk_gemini_support=1
persist.radio.gemini_support=1
ril.current.share_modem=2
ro.mtk_audio_profiles=1
ro.mtk_audenh_support=1
ro.mtk_besloudness_support=1
ro.mtk_bessurround_support=1
ro.mtk_wapi_support=1
ro.mtk_bt_support=1
ro.mtk_wappush_support=1
ro.mtk_agps_app=1
ro.mtk_audio_tuning_tool_ver=V1
ro.mtk_wlan_support=1
ro.mtk_ipo_support=1
ro.mtk_gps_support=1
ro.mtk_omacp_support=1
ro.mtk_search_db_support=1
ro.mtk_dialer_search_support=1
ro.mtk_dhcpv6c_wifi=1
ro.have_aacencode_feature=1
ro.mtk_fd_support=1
ro.mtk_oma_drm_support=1
ro.mtk_cta_drm_support=1
ro.mtk_widevine_drm_l3_support=1
ro.mtk_eap_sim_aka=1
ro.mtk_fm_recording_support=1
ro.mtk_audio_ape_support=1
ro.mtk_flv_playback_support=1
ro.mtk_wmv_playback_support=1
ro.mtk_send_rr_support=1
ro.mtk_emmc_support=1
ro.mtk_tetheringipv6_support=1
ro.mtk_shared_sdcard=1
ro.mtk_2sdcard_swap=1
ro.mtk_enable_md1=1
ro.mtk_flight_mode_power_off_md=1
ro.mtk_aal_support=1
ro.mtk_pq_support=2
ro.mtk_miravision_support=1
ro.mtk_miravision_image_dc=1
ro.mtk_wfd_support=1
ro.mtk_wfd_sink_support=1
ro.mtk_wfd_sink_uibc_support=1
ro.mtk_wifi_mcc_support=1
ro.mtk_thumbnail_play_support=1
ro.mtk_bip_scws=1
ro.mtk_world_phone_policy=0
ro.mtk_perfservice_support=1
ro.mtk_cta_set=1
ro.mtk_mobile_management=1
ro.mtk_antibricking_level=2
ro.mtk_cam_mfb_support=3
ro.mtk_slow_motion_support=1
ro.mtk_lte_support=1
ro.mtk_cam_vfb=1
ro.mtk_rild_read_imsi=1
ro.sim_refresh_reset_by_modem=1
ro.mtk_bg_power_saving_support=1
ro.mtk_bg_power_saving_ui=1
ro.have_aee_feature=1
ro.sim_me_lock_mode=0
ro.mtk_dual_mic_support=0
ro.mtk_is_tablet=0
wfd.dummy.enable=1
ro.mediatek.project.path=device/tinno/p6601
persist.mtk.wcn.combo.chipid=-1
service.wcn.driver.ready=no
service.wcn.coredump.mode=2
ro.com.android.mobiledata=false
persist.radio.mobile.data=0,0
persist.meta.dumpdata=0
mtk.vdec.waitkeyframeforplay=1
ro.myos.release.apk=1
ro.project=blu_us
ro.target=p6601
ro.subproject=persist.sys.dalvik.vm.lib.2=libart
dalvik.vm.isa.arm.variant=cortex-a53
dalvik.vm.isa.arm.features=default
net.bt.name=Android
dalvik.vm.stack-trace-file=/data/anr/traces.txt

# begin fota properties
ro.fota.platform=MTK6735_6.0
ro.fota.type=phone
ro.fota.app=5
ro.fota.oem=tinno6735_6.0
ro.fota.device=R1_HD_R0010UU_GENERIC
ro.fota.version=BLU_R0010UU_V6.1_GENERIC_6.0_20160617-1456
# end fota properties
ro.expect.recovery_id=0x7ba5bb9dd9b238b42d7097670788f53a12aa6521000000000000000000000000

fastboot getvar all

(bootloader) max-download-size: 0x8000000
(bootloader) partition-size:flashinfo: 1000000
(bootloader) partition-type:flashinfo: raw data
(bootloader) partition-size:userdata: 32000000
(bootloader) partition-type:userdata: ext4
(bootloader) partition-size:cache: 19000000
(bootloader) partition-type:cache: ext4
(bootloader) partition-size:system: a7000000
(bootloader) partition-type:system: ext4
(bootloader) partition-size:metadata: 2500000
(bootloader) partition-type:metadata: raw data
(bootloader) partition-size:nvdata: 2000000
(bootloader) partition-type:nvdata: ext4
(bootloader) partition-size:frp: 100000
(bootloader) partition-type:frp: raw data
(bootloader) partition-size:tee2: 500000
(bootloader) partition-type:tee2: raw data
(bootloader) partition-size:tee1: 500000
(bootloader) partition-type:tee1: raw data
(bootloader) partition-size:keystore: 800000
(bootloader) partition-type:keystore: raw data
(bootloader) partition-size:secro: 600000
(bootloader) partition-type:secro: raw data
(bootloader) partition-size:oemkeystore: 200000
(bootloader) partition-type:oemkeystore: raw data
(bootloader) partition-size:seccfg: 80000
(bootloader) partition-type:seccfg: raw data
(bootloader) partition-size:expdb: a00000
(bootloader) partition-type:expdb: raw data
(bootloader) partition-size:logo: 800000
(bootloader) partition-type:logo: raw data
(bootloader) partition-size:recovery: 1000000
(bootloader) partition-type:recovery: raw data
(bootloader) partition-size:boot: 1000000
(bootloader) partition-type:boot: raw data
(bootloader) partition-size:para: 80000
(bootloader) partition-type:para: raw data
(bootloader) partition-size:lk: 80000
(bootloader) partition-type:lk: raw data
(bootloader) partition-size:protect2: a00000
(bootloader) partition-type:protect2: ext4
(bootloader) partition-size:protect1: a00000
(bootloader) partition-type:protect1: ext4
(bootloader) partition-size:nvram: 500000
(bootloader) partition-type:nvram: raw data
(bootloader) partition-size:proinfo: 300000
(bootloader) partition-type:proinfo: raw data
(bootloader) partition-size:preloader: 40000
(bootloader) partition-type:preloader: raw data
(bootloader) off-mode-charge: 1
(bootloader) warranty: yes
(bootloader) unlocked: no
(bootloader) secure: yes
(bootloader) kernel: lk
(bootloader) product: P6601
(bootloader) version-preloader: 0.1.00
(bootloader) version: 0.5

The next step is to compile a custom recovery, and attempt to boot it :

adb reboot-bootloader twrp_R1_HD.img [B](does not exist yet !!!)[/B]
fastboot boot