Is it intended for a lvl20 moon druid to full heal by shifting from 1 form to another?

Does Sanctuary end when Spirit Guardians deals damage to enemies?

Divine Smite is for ‘melee weapon attacks’ so is it ok for my Monk/Paladin to use with Unarmed Strikes?

According to the Official Sage Advice Compendium:
Can a paladin use Divine Smite when they hit using an unarmed strike? No. Divine Smite isn’t intended to work with unarmed strikes. Divine Smite does work with a melee weapon attack, and an unarmed strike can be used to make such an attack. But the text of Divine Smite also refers to the “weapon’s damage,” and an unarmed strike isn’t a weapon. If a DM decides to override this rule, no imbalance is created. Tying Divine Smite to weapons was a thematic choice on our part—paladins being traditionally associated with weapons. It was not a game balance choice.

What does “Initiative count 20” mean?

Is the damage type of Hunter’s Mark the same as the damage type of the weapon?

If you cast from a Staff of Power does concentration come from you or the staff?

Hellish Rebuke as a racial spell, does this spell use up one of my spell slots?

Would it stand to reason that deafness could impair spellcasting?