do dungeons respawn and if they do how do i stop them from respawning (without mods)

Basically all the Creatures respawn. (in 72 game hours if you do not 'Dispose of Corpse' ... But as soon as you leave and reenter the cell if you did 'Dispose' )
There is no way to prevent this.

NPCs do not respawn. (except Guards, but they don't appear in dungeons)

Containers will respawn new items in 72 game hours after you leave the cell, unless you add or remove anything from the container. Then the items remain the same for ever.