Kali linux

If i put kali linux on a sd chip and insert that into my bbb, from what i read ill be able to run kali. From what i understand the process is similar to have a bootable usb. If thats the case will i go back to whatever version of linux is flashed on the bbb if i take the sd chip out?

You do need to make sure that Kali is compiled for the ARM and that it has the right kernel modules to support the beaglebone hardware.

I know from experience that you can crosscompile the stable kernel for beaglebone black, but the custom kernel that is used in the beaglebone image has better hardware support.

When you power the beaglebone you hold the button near the SD card to force booting from the SD card.
By default, it will boot the internal eMMC.
If you write some zeros to the eMMC, such that it cannot boot, the beaglebone would continue to boot the SD card after failing to boot from eMMC.
You can always use an SD card to reimage the eMMC.