I read that dungeons are locked at the level when you first enter them. So let's say I enter a dungeon at level 2 and then later on in the game I do a random quest (the ones you get from the inn keepers) and it sends me back to that dungeon when I am at level 45 (because I have already been to all the dungeons at this point). Will the dungeon level reset at this point with the automatically create quest system?
A dungeon is set at the level when you first enter, some dungeons however may have a minimum level and if you enter at a level lower then that it is set at its minimum.
An example could be a level 5 character enters a dungeon and all the monsters inside are set at an equivalent level lets say 4-6. That same character could enter another dungeon still at level 5 but it has a minimum level of 10, therefore the monsters are set to what a level 10 would find in a dungeon.
Enemies are reset once a week even in dungeons you have cleared. I am not sure if that alters the dungeons that you have entered and then left.
I've been told (a.k.a. no reliable sources) that dungeons reset every 7 days. When you enter a dungeon that has been reset, it will spawn new level appropriate enemies. I'm not sure how this is impacted by a dungeon being 'cleared' though...
So I decided not to be completely lazy and did a quick Google search. This is a second-hand quote, referring to the game guide, which I do not own, so take it as you will.
my guide says that most dungeons will repopulate over time. It says maybe a little over a week for a location you left midway through or perhaps a month or more for a location you've cleared.