Or just wait a few more days for your local consulates to clarify what kind of proof they accept. I also believe certain minimums of “soft power” activities will have to be met. But in general, yes: you attend something for a few months but will get a 5 year visa. That is what it is.
Not true. 180 days out and back in as often as you like. Or optionally 180 days + another 180 days extension possible at every entry. Please read the extensive information and laws I shared in previous posts.
An extension is an additional time allowed in Thailand without having to leave the country and return. You pay for that extension at an immigration office within Thailand and they give you a new stamp in your passport so that you can stay longer. You can do that once for every time you entered Thailand.