This is a pretty funny question... But to answer it again.
Yes, you can go in reverse. It's no different than going forward...
4h can be engaged at any time. As long as you are under 50mph you can shift in and out of 4h on the fly (its also best to be off the throttle...) Don't worry though, the computer won't let you hurt it.
The only thing you really need to remember is that you don't want to be driving on dry pavement and making sharp turns (in forward or reverse) while in 4wd as this will cause binding between the front and rear drive shafts trying to move at different speeds. It's fine on slick surfaces, because the tires will slip and there will be no binding. There is no center differential in a part time 4wd system, so both drive shafts must turn at the exact same speed.
It's actually fine to be in 4wd on patches of dry pavement, but the rule of thumb I use is that if the turn could be made at ~30mph then it is fine to stay in 4wd. If I would normally have to be going slower to make such a turn, I flip it back to 2h. I've never had a binding issue following this rule of thumb on dry pavement.