What Happeneds if i jailbreak my iphone and it freezes and/or doesn't work?

Like, could it be restored so all of my stuff was still on there?
if so how?

if my stuff couldnt be restored could i refomat the phone so it still works?
if so how?

Just make sure you do a backup/sync before jailbreaking (99.9% safe) and you will be able to recover if things go wrong, which they won't.

:)

An iTunes restore will wipe the phone back to un-jailbroken state.

It is safe, but, as with anything, rather its a pc, mac, droid or iphone, you need to back it up before you don anything, so that way if anything goes wrong, it can be fixed easily

Yes you can always restore with itunes.