Hi,

1. Basically: A. Don't be an ass. B. Don't be a douche. C. Do. Not. Use. TNT. (= Autoban) D. Don't cheat or exploit bugs.

2. Wherever you can build and where there is space. You can go back to the boat with /spawn, to set your own homepoint do /sethome THEN you can use the /home command.

3. You can buy stuff when I am online, you can visit the shop though to check prices: /warp shop

4. Nope, just go with the most recent version of Minecraft.