all that is known would be in this site's pages. if the info is not there, it is probably unknown.

about Odin using Mjolnir, I did not find any mention of that on his page. also did not find Odin in the list of users on Mjolnir's page.

I would assime for the second question that there was no worthiness enchantment. Probably anyone could’ve wielded it if they were powerful enough and knew how to use it.

1. No, Hela was the first to wield Mjolnir.

2. Yes but anyone could use the lighting just like Steve did in Endgame, Odin put that enchantment just to make sure that Thor's Ego at the time which was massive didn't get in the way of learning a lesson.

3. Probably based on Thor's personality during the comic. I never actually fully read it but what I Can Remember Thor's Personality was similar to how he was during the beginning Thor 1.

@Mdsb759 it’s on Mjolnir’s page my bad

checked again; Odin was in the list of users.

Prior to 2011, yes anyone could have used the hammer and the lightning powers come with it ish after Ragnarök Thor could use the powers without the hammer.