Well, it depends if you are your own friend
Most of the time if a spell affects a model/unit then the caster will also be able to use it on himself. Except if it says for instance target warjack.
As for the second Q it depends on what spell or feat is used. for instance Striker has Earthquake and that knocks down all models in the area. but some casters have spells that will effect any enemy in the area.
It is spell related. Read the card and it should be clear. if not post it in her and we will try and help...