can I reset quests?

I need to reset two quests.

Ominous Altars - died on boss, went away, did other stuff, came back, now the boss altar is locked behind a smoke tornado, I cant summon boss, cant complete quest.

Act 1 final boss - I killed it but then died. No loot, no MPC putting it to sleep etc. but quest had advanced and now I am on Act 2. I want to re-do it.

Is there a way to reset quests?

As far as I'm aware the only way to reset a quest is to roll a new character - and the quest to acquire Renly's tools will not reset. All subsequent characters will already have access to the salvage bench.

But for the second case at least, spawning a new instance of the manor and killing Geonor again will play the cutscene again.

My brain derped. Ominous Altars is the one in Freythorn, right? If you didn't kill the boss, you may also be able to reset the instance and do the whole zone again to fight him.