if we get banned, what would be our limitations? can we still play with the same account and post on forums and buy and sell some items?

Nope,

BAN - not allowed.

So basically, if you get banned you won't be able to access toribash at all.
You can be:

perma-banned [ permanent ban] - meaning that the account that was "perma banned" cannot access toribash at all,
meaning that the ban will never be lifted.

or

Just banned - This ban will be lifted after some time.

You can use another account as the bans don't affect your other alt accounts.

There are other tips of bans such as a Market ban.

You can get a market ban if you don't obey the rules
and get many infractions.
This type of ban can or cannot be lifted.

So i suggest that you should read the rules.

All i can say is getting banned is really shameful, but not for those people who don't care about thier fame.