Hey i was wondering that could i play LFS on different computers like if im licensed as S2 on a computer then i try to login on another computer with that same account would it work?

It will only work on a LAN game, that's not using the master server.

Yea but like only to use single player.I mean it like i dont have to lock my LFS to demo then i can login with the account to use single player.

you can, but only if its your computer.