1. Sure - all five senses, maybe more
2. For me rarely - and v.mild
3. Yes - like Bortolazzo said. The fantasy can even be better than the reality!
4. From dreamy/foggy to hyper-lucid larger-than-life.
5. No more danger than regular dreaming. Some mild frustration can occur during a dry spell. There's a theoretical 'risk' of becoming obsessed / addicted if you have that personality type (which is true for pretty much anything). You may also bore your friends with tales of your nocturnal adventures. Some may get jealous - others may even worry that you are doing something freaky/cultish.

Search the forums - all these questions have been discussed at length, with much better answers than I've given here.

Oh - and welcome