So for cards such as {suffering} can you cast both or just one of the spells?
For split cards like {Pain} // {Suffering}, you can cast one side, or the other. But only one side at a time.
They have some pretty funky rules when it comes to checking their converted mana cost (CMC) and such, but generally think of them as two separate spells.
Ah okay so only one from a twin card. So once you cast one side, the other is lost to the graveyard.
Yep.
But as we've seen, things in the graveyard aren't always lost. ðŸ'€
Very true.. Where can I find a banned/restricted list for vintage?
Here:
http://www.wizards.com/Magic/TCG/Resources.aspx?x=judge/resources/banned