90 day reports are for basically any stay in Thailand of 90 days irregardless of which visa. But no, you don't have to supply the same information as when you get the DTV.
The 90 day report is simple with a few pieces of paperwork. The purpose is to update immigration with where you are living and is not related to the visa.
You can stay up to 180 days (it doesn't matter how many), then leave the country and return and get a new 180 stamp each time. Easy, I've already done it.
Extension- still unknown what the requirements will be
1) It depends on which embassy you apply through. Some require 6 months, some only current account balance.
2) First point to bring up is extension versus reentry. No one has extended yet and so not sure what will be required for an extension. If you leave the country and re-enter then nothing is required. Every time you enter you get 180 day stamp. (I have already done this)
Agree with Ron. The shop right inside together with immigration was very helpful. My fee was only 150 baht with them.
the inspection is very basic - check to make sure basic things work like turn signals and stuff.
Insurance - get it once the blue book title is in your name.
One more piece of advice - if you want to simplify things and not go all the way to DLT. There is a registration and inspection station in Jomtien off of Threppasit road. Costs an extra 1000 or so but no lines and they handle everything. They can also do the insurance
Anonymous participant I was being sarcastic. Because what would we expect to happen.... I ask random people on fb and then I'm supposed to tell the Thai government officials that they are doing their job incorrectly and to do it the way that some ransom guy on fb says it should be done. I'm sure the government officials will say "I'm sorry, thanks for teaching me how to do me job..."