Short answer, yes you can. You can do anything the camper features allow while it is in the truck. It’s designed more to be used IN the truck than out of it. However most campers function virtually the same out of the truck.
Sorry if we’re acting as if this is a strange question. But It is. Not as strange as the thread goin on the the Class C forum right now, but maybe I’m a little shell shocked from that one! Lol
And fwiw, I’ve never once found the slightest reason to even loosen the tie downs unless unloading.
Get the truck halfway level with a few boards or blocks and then use the rear jacks to adjust a tad more while taking up a bit of the weight to also stabilize the camper. (Which should feel relatively solid compared to some setups based on your truck, your camper AND having a trailer hooked.)