I'm looking at getting a Ball Python but had some questions first.

I'm getting a 20gal long tank my sister used to have her red tailed boa in and will probably be using shredded aspen for bedding, but may move to astro turf later. Can a BP stay in a 20 gal long its whole live?

I'm a little confused about how feeding works, I've read its better to move the snake to a different box for feeding so it doesn't assume everything that reaches into the tank is food. Then I read that you aren't supposed to handle the snake for a couple days after feeding it, so does this mean that I should feed the snake and then give it like 30 min to digest and then put it in the tank and leave him alone?

I feel like I have more questions but I can't think of them right now, so any tips would be appreciated.
Thanks!

Also for feeding how often should a young BP be fed? One mouse every 5-ish days? I don't want to fast track the growth rate because I've heard that can shorten their lifespans.