Cleric 2/Wizard 2 finds a 2nd level spell in a book, can he copy 2nd level wizard spell into his book?

Does necromancers undead minions heal on short and long rests, like a character?

Are material components always consumed upon casting?

Does a fighter with an increased crit range (say 19-20) always hit on a 19?

Can you jump farther than your movement when using Jump & Boots of Striding and Springing?