[Xperia Z3 Tablet Compact General] alex9x:
by the way... trying to fastboot original secured bootimg... downloaded this files:

amss_fsg_S1-MODEMSW-LIVE-9C84-PID1-0006-MMC.sin
amss_fs_1_S1-MODEMSW-LIVE-9C84-PID1-0006-MMC.sin
amss_fs_2_S1-MODEMSW-LIVE-9C84-PID1-0006-MMC.sin
apps_log_S1-SW-LIVE-9C84-PID1-0006-MMC.sin
b2b_S1-SW-LIVE-9C84-PID1-0006-MMC.sin
cache_S1-SW-LIVE-9C84-PID1-0006-MMC.sin
cust-reset.ta
elabel-SGP621-row_201410031119.1_23.0.1.A.0.167_S1-ELABEL-LIVE-9C84-PID1-0004-MMC.sin
fota-reset.ta
fotakernel_S1-SW-LIVE-9C84-PID1-0006-MMC.sin
kernel_S1-SW-LIVE-9C84-PID1-0006-MMC.sin
loader.sin
partition-image_S1-SW-LIVE-9C84-PID1-0006-MBR.sin
simlock.ta
system_S1-SW-LIVE-9C84-PID1-0006-MMC.sin
update.xml
userdata_S1-SW-LIVE-9C84-PID1-0006-MMC.sin

and folder boot:

boot_delivery.xml
dbi_S1_Boot_MSM8074AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B70E1-SWID12-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
dbi_S1_Boot_MSM8074AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B70E1-SWID12-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
dbi_S1_Boot_MSM8274AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B60E1-SWID12-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
dbi_S1_Boot_MSM8274AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B60E1-SWID12-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
dbi_S1_Boot_MSM8974AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B40E1-SWID12-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
dbi_S1_Boot_MSM8974AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B40E1-SWID12-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
emmc_appsboot_S1_Boot_MSM8074AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B70E1-SWID09-OEM0-AID1-DEBUG00-S1-BOOT-TEST-B316-0001-MMC.sin
emmc_appsboot_S1_Boot_MSM8074AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B70E1-SWID09-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
emmc_appsboot_S1_Boot_MSM8274AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B60E1-SWID09-OEM0-AID1-DEBUG00-S1-BOOT-TEST-B316-0001-MMC.sin
emmc_appsboot_S1_Boot_MSM8274AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B60E1-SWID09-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
emmc_appsboot_S1_Boot_MSM8974AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B40E1-SWID09-OEM0-AID1-DEBUG00-S1-BOOT-TEST-B316-0001-MMC.sin
emmc_appsboot_S1_Boot_MSM8974AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B40E1-SWID09-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
rpm_S1_Boot_MSM8074AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B70E1-SWID0A-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
rpm_S1_Boot_MSM8074AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B70E1-SWID0A-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
rpm_S1_Boot_MSM8274AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B60E1-SWID0A-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
rpm_S1_Boot_MSM8274AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B60E1-SWID0A-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
rpm_S1_Boot_MSM8974AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B40E1-SWID0A-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
rpm_S1_Boot_MSM8974AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B40E1-SWID0A-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
s1sbl_S1_Boot_MSM8074AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B70E1-SWID65-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
s1sbl_S1_Boot_MSM8074AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B70E1-SWID65-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
s1sbl_S1_Boot_MSM8274AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B60E1-SWID65-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
s1sbl_S1_Boot_MSM8274AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B60E1-SWID65-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
s1sbl_S1_Boot_MSM8974AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B40E1-SWID65-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
s1sbl_S1_Boot_MSM8974AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B40E1-SWID65-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
sbl1_S1_Boot_MSM8074AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B70E1-SWID00-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
sbl1_S1_Boot_MSM8074AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B70E1-SWID00-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
sbl1_S1_Boot_MSM8274AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B60E1-SWID00-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
sbl1_S1_Boot_MSM8274AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B60E1-SWID00-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
sbl1_S1_Boot_MSM8974AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B40E1-SWID00-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
sbl1_S1_Boot_MSM8974AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B40E1-SWID00-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
Scorpion_S1BootConfig_MiscTA.ta
tz_S1_Boot_MSM8074AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B70E1-SWID07-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
tz_S1_Boot_MSM8074AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B70E1-SWID07-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
tz_S1_Boot_MSM8274AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B60E1-SWID07-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
tz_S1_Boot_MSM8274AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B60E1-SWID07-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin
tz_S1_Boot_MSM8974AC_LA3_0_55_AID_1_MSM8974AC-TEST-HWID007B40E1-SWID07-OEM0-AID1-DEBUG00_S1-BOOT-TEST-B316-0001-MMC.sin
tz_S1_Boot_MSM8974AC_LA3_0_55_AID_4_PLATFORM-MSM8974AC-LIVE-HWID007B40E1-SWID07-OEM1-AID4-DEBUG00_S1-BOOT-LIVE-9C84-0004-MMC.sin

How to make boot.img from this set from sony site? from kernel I`ve got elf and from it - kernel+dt+ramdisk.

For my experiment I use bootimg.zip from miui.com site, it work in folder, and I unpack 611 from this forum (working boot image) and mix with kernel+ram+dt extracted from original firmware from kernel elf.

Or maybe any manual to get 621 original boot.img....