Never been allowed to disembark from the rear hatch even if there was one. The umbilical is always attached to the front.

This all depends on the slot of the plane. If it's directly connected to the terminal, you can exit from the front only. If it's free standing and you need to walk over the tarmac or take a bus to the terminal, you can disembark from the rear because then they will open the rear exit as well. Ironically this means that with budget flights you disembark faster because they don't tend to pay for the premium slots that are directly at a terminal.

The type of plane, whether it's a 737 or A320 or whatever, rarely matters.

I cannot remember the last time I exited through the back. I have not flown as much but for the last 10 years about 4-6 flights per year and I think I went out the back maybe once in Greece. But I am not sure might just be misremebering.