Questions regarding effects and cost

When a destroyed spirit is revived directly to the field via an effect like ElecticFairy Birit's, does the cost need to be payed again, and does the <When Summoned> effect activate again? Additionally, if the spirit is sent to the trash via deck destruction, does it qualify as "destroyed"?

For effects that remove magic from play in cards like depicted with Magic Book, can the magic be used only once or multiple times? Must the cost be payed each time? Would the cards count as part of the hand for effects such as that of The FairyPriest Andromeda?

No, for effects that returns or have your spirits remain on the field, you don't have to pay their cost again also, it's not a summon so you cannot activate their (When Summoned) effects. Additionally, you cannot use the destroyed card's (When destroyed) effects if you want to return/have them remain on your field.

Cards like Magic Book removes your card but when you use them, they are treated as used from your hand, therefore The FairyPriest Andromeda's effect is applicable. However, you cannot set removed burst cards. Also, after using the spell, it is sent to the trash like normal, unless if you have effects like Brilliance which returns it to your hand at the end of the battle.

Ah, I see. Thanks very much for clearing that up!