Do lairs having been cleared out become cleared because for me it doesnt say cleared so do they just respawn a couple of days later ?

I'm pretty sure everything respawns eventually and the "Cleared" tag is just to indicate you've been there and killed everything.

Some don't ever have the cleared tag. Not sure what it is.

I Know that the caves have the cleared tagged but i cleared out a lair and it didnt come up and i was like hmmmmm what am i missing e.g Movarths lair

Movath lair should clear later, because parts of it are blocked off and reserved for a quest. but there are other areas that won't clear. Example: Irkngthand & Swindler's den.

Ahhh ok thank you