Ok what I know is someone teferi's protection but i have in play something like Questing Beast or casting a sorcery/instant like Skullcrack I’m aware stuff with Infect or commander damage will still kill them with prevention effects since your not really reducing the life
What I’m checking is combat damage stuff will still trigger and stuff like this will also kill them which is…
(And with the conditions met ofcoarse)
Any effects on those aforementioned cards that require combat damage to be dealt will not trigger/function. Teferi's Protection grants the caster "protection from everything", which in essence means that no combat damage will be dealt to the caster (unless that damage cannot be prevented).
With Angel of Destiny you will not be doing damage to the player but if your life total meets the requirement then that opponent will lose the game. All the other cards on the list however will not work.
With Questing Beast the damage will still be dealt however the damaged player's life total will not change. But any triggers that result from damage being dealt would trigger as normal.
if i had Questing beast in play and attacked a teferi'd person with Phage the Untouchable (or any of the other 3 cards besides the angel) would it cause them to lose because the damage can't be prevented and combat damage effects would trigger.
If the damage cannot be prevented, then Teferi's Protection's protection doesn't prevent it, so it is dealt. So Vorpal Sword, Strixhaven Stadium, or Phage the Untouchable would trigger. If Questing Beast is the out, then Atemsis can only deal combat damage to your opponent, so its triggered ability can only trigger that way.