Can you activate Michizure when they activate Sak Armor, Mirror Force, or Widespread Ruin?

yes. you can use michizure at any time except in the damage step. those traps are used in the battle step so michizure is fine.

And, at least based on previous threads, if the monster hitting the Graveyard is the very last thing to occur.

yes, similar to using BTH on a monster summoned during a chain. BTH can only be used if the last effect was the summon.

if the chain happened to be "graceful charity" -> "call of the haunted" then graceful would resolve last and you wouldn't be able to use BTH.

however if the chain was "call of the haunted" -> "jar of greed" then the last thing to resolve would be call summoning a monster and BTH could be used. (hence you can only respond to the last action of a chain)

this is also shown in the complex activation timings of appropriate and forced requisition. where if the last effect was graceful charity, forced requisition could be activated(fliped face up) but appropriate couldn't (since the last action was a discard not a draw)

...heh, i was originally going to disagree with your HDI, i always get confused being able to activate your response at any time in the current chain, and only being able to respond to the last part of the previous chain.

Yeah...that's why, contrary to what a lot of "mature" people think, Yu-Gi-Oh! is far from "a game just for little kids", lol

it is a game for little kids, it was just designed by a bunch of rocket scientists and mental patients. :p

More like a 13+ game really...it was mainly just dumbed down when it came out here, though...all the name changes, picture changes and everything.