1. Text base combat with the dice roller of course, so movement won't  be a thing in this, but there will still be opportunity attacks, advantage on flanking, etc.

2. Depending on if it's in the core DM,  I don't have the other books, and I know you can get them thru pdf, I just don't have the room on this tablet.

3. If you wanna play 3 halfling characters...you can, if they plan on standing on each other's shoulders, it'll be a lot of Dex. Checks 😃 and don't get me started if they try combat that way, gonna be high DC checks, so u better make sure to have Acrobatics.

As for the other two things, that's a No.