Mystical Space Typhoon resolves, destroying 1 Spell or Trap card on the field.
Offering to the Snake Deity resolves, destroying all 3 targets if they are all on the field (if one was destroyed by MST, it will not destroy anything).
Dark Hole resolves destroying all remaining monsters on the field.
All cards involved in a chain that are temporary cards such as non-Continuous Spell/Trap cards, remain on the field until the chain has resolved, unless an effect within the chain (or payment of a cost) would cause that card to be removed from the field (Ex. MST chained to Upstart Goblin, Upstart activates, MST chains, MST destroys Upstart, Upstart resolves, draws user 1 card and their opponent gains 1000 LP, chain ends, MST goes to Grave.)