most country are visa exempt for 60 days currently, suggestions are that this may reduce to 30 days at some point in the future. The 60 days can be extended for another 30 days at a local immigration office
you may well be correct but it doesn't really matter, the only thing that matters is what the thai authorities consider. So in this instance just use your passport country of origin otherwise at present they won't let you in
it looks like that could be true as its typically when you enter thailand but until the rules have been released and we can all see what the expectations are it's hard to say. You wont need it this time on your way in but just keep an eye out when you are in phuket
if you look at the mandatory fields , which includes a very detailed thai address not just hotel x in bangkok, I'm sure many travellers won't know what to put so will not be able to submit the form!!! I think many queues will be forming at immigration