As for whether you can open the bed-end while still hooked up, there are a few considerations. One, if you're at a truck-stop or a parking lot, it's would seem rude to do so. In those instances, we just sleep on the dinette bed. Next, if your site isn't level, you may have a problem with your refrigerator. Ours demands to be perfectly level, front to back. It's hard to level a camper while it's still attached.
Parking and backing up - OY! I don't know how to do it, no matter how hard I've tried. I usually travel with someone who knows how or else I use a pull-through site. I intend to keep practicing, though. I have a patient brother who's willing to teach me.