[Sony Xperia XZ1  Questions & Answers] pbarrette:
I have an XZ1c, but have not unlocked my bootloader at this time.

As for your questions:

1] The XZ1 and XZ1c do have a vbmeta partition.

2] The devices do not have A/B system partitions.

3] Firmware for the phone, which includes the boot image can be downloaded with the XperiFirm software.

3b] The software will download and extract multiple "*.sin" files (signed sparse images) which can be extracted to full images with UnSIN.

The Sony "boot" images are named "kernel_X-FLASH-ALL-XXXX.sin" where "XXXX" is a device dependent identifier.

It is a 20MB, standard android image which contains a 14MB kernel zImage and a ~5.5MB gzipped CPIO ramdisk.

EDIT: Here's a list of the partitions on the phone:

0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 FOTAKernel -> /dev/block/sda47
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 LTALabel -> /dev/block/sda2
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 Qnovo -> /dev/block/sda60
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 TA -> /dev/block/sda1
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 abl -> /dev/block/sda11
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 ablbak -> /dev/block/sda12
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 apdp -> /dev/block/sda40
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 appslog -> /dev/block/sda58
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 bluetooth -> /dev/block/sda39
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 boot -> /dev/block/sda38
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 cache -> /dev/block/sda53
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 cmnlib -> /dev/block/sda16
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 cmnlib64 -> /dev/block/sda18
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 cmnlib64bak -> /dev/block/sda19
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 cmnlibbak -> /dev/block/sda17
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 ddr -> /dev/block/sda48
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 devcfg -> /dev/block/sda21
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 devcfgbak -> /dev/block/sda22
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 devinfo -> /dev/block/sda13
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 diag -> /dev/block/sda59
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 dpo -> /dev/block/sda42
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 dsp -> /dev/block/sda37
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 frp -> /dev/block/sda56
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 fsc -> /dev/block/sda51
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 fsg -> /dev/block/sda34
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 fsmetadata -> /dev/block/sda61
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 hyp -> /dev/block/sda7
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 hypbak -> /dev/block/sda8
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 keymaster -> /dev/block/sda14
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 keymasterbak -> /dev/block/sda15
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 keystore -> /dev/block/sda55
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 limits -> /dev/block/sda44
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 logfs -> /dev/block/sda46
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 misc -> /dev/block/sda54
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 modem -> /dev/block/sda36
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 modemst1 -> /dev/block/sda49
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 modemst2 -> /dev/block/sda50
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 msadp -> /dev/block/sda41
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 oem -> /dev/block/sda63
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 persist -> /dev/block/sda33
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 pmic -> /dev/block/sda9
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 pmicbak -> /dev/block/sda10
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 rdimage -> /dev/block/sda62
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 rpm -> /dev/block/sda3
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 rpmbak -> /dev/block/sda4
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 sec -> /dev/block/sda35
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 splash -> /dev/block/sda43
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 ssd -> /dev/block/sda52
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 sti -> /dev/block/sda20
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 storsec -> /dev/block/sda23
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 storsecbak -> /dev/block/sda24
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 system -> /dev/block/sda65
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 toolsfv -> /dev/block/sda45
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 tz -> /dev/block/sda5
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 tzbak -> /dev/block/sda6
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 tzxfl -> /dev/block/sda29
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 tzxflattest -> /dev/block/sda27
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 tzxflattestbak -> /dev/block/sda28
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 tzxflbak -> /dev/block/sda30
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 userdata -> /dev/block/sda66
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 vbmeta -> /dev/block/sda57
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 vendor -> /dev/block/sda64
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 xbl -> /dev/block/sdb1
0 lrwxrwxrwx 1 root root 15 1970-01-31 19:27 xblbak -> /dev/block/sdc1
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 xfl -> /dev/block/sda25
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 xflbak -> /dev/block/sda26
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 xflkeystore -> /dev/block/sda31
0 lrwxrwxrwx 1 root root 16 1970-01-31 19:27 xflkeystorebak -> /dev/block/sda32