Greetings. I love the Cape Cod National Seashore! I've spent a week in the Cape every July since 1996. Here's a link to the NPS website for the Cape Cod National Seashore where I got information about getting my oversand permit.
http://www.nps.gov/caco/planyourvisit/permits.htmIf you click the "contact us" link or call the Ranger Station by phone, it puts you in direct contact with an NPS Ranger and they are always very, very helpful and friendly. I'm sure someone there could answer the questions you listed above with little trouble.
I only have experience with the Cape Cod National Seashore and no other ORV management plans. However I can tell you that the NPS at Cape COd has their proverbial sh*t together and they are very thorough, knowledgeable and experienced in managing the seashore. I think you'll find that the Cape Cod National Seashore is one of the nation's first (if I remember correctly) and they've been dealing with the management and protection of the seashore for many years. They have it down to a science. If you'd like to use some of my photos from the Cape ORV route, feel free. Here they are:






Good luck and let me know if you have any other questions!