Yes

Yes they do all have 30 amp.

Lots of them are 50/30A sites. Great location.

Yes.

I have a 50 amp rig. I use a pigtail adapter to convert a 30 amp or regular 15-20 amp house outlet to a 50. Should be able to go the other direction. The specific answer to your question is that I don't remember exactly. I did see other rigs in the park using 30 amp and plain old extention cords.

Yes, I believe so, but visit the web site to be sure.