You can't cast more than one spell each turn.
You may play lands and cast spells from your graveyard.
If a card would be put into your graveyard from anywhere, exile it instead.
It will exile itself if it is going to the graveyard from the battlefield.
The cards in your graveyard are not considered to be in your hand for any reason. For example, you can’t discard them.
You count spells that were cast this turn before this card enters the battlefield. (The Invasion FAQ is not correct on this point.)