I have a 100 warrior with 83 in cleric and 40 in mage

My question is, as I level other schools, how can I see what spells and abilities I can use to level with? When I switch to Cleric I can cast all my heals and buffs, but when I switch to mage, they are grayed out, even though I have the requisite Life skill. Also, when in Cleric school, my Mage spells/abilities aren't available. I understand that only mastered abilities can be used in other schools, but what about spells?

Is there a guide that explains what skills and abilities can be used while leveling multiple adventure classes?