-If Gambit charged Mjolnir wit energy and let go? (would Mjolnir be destroyed?)
No, Mjolnir would absorb anything Gambit tries to charge it with
-If Galactus blasted Sinister? (would Sinister regenerate?)
Sinister wouldn't have anything to regenerate from
-If Juggernaut ran into the Blob (would Juggernaut stop?)
No, he'd probably be redirected though.
-If Mjolnir was on a piece of steel, could u pick up the steel, therefore lifting Mjolnir if u werent worthy?
You won't technically be lifting Mjolnir. If Juggernaut lifted Thor, he's not actually lifting Mjolnir, the hammer just happens to be with Thor. Like if Mjolnir was on a table, you could lift the table with Mjolnir on it, I wouldn't think it's cause for celebration though and go "I'm worthy!!"