Prompt How to reboot into stock recovery

I want to reboot into recovery using adb
when trying

adb reboot recovery

or

adb shell reboot recovery

it reboots into android system (not the recovery)

when trying

echo -en "boot-recovery\0" > /dev/block/nandf; sync; reboot

it reboots into recovery but only recovery background logo without recovery options

so i thought that there is no stock recovery

buuuuuuuuuuuuuuuuut

i flashed FaaastJB firmware for A13

and reflashed the dumped stock recovery.img

tried the ways above with same result

the surprise is FaaastJB has option boot into recovery in backup/restore
it boots into stock recovery yeeeeeeeeees there is a stock recovery

the question is Hooooooow FaaastJB do it???? or even how to do something like that

Thanks in Advance