Government regulations require the hotels to refund the RT-PCR test, SHA transport, and hospital fees I'm the event of a regulation change. Decline their offer, demand a refund.
Yes, they ask for insurance at the airport. If you only have insurance for 3 months, you'd only be stamped in for 3 months (most of the time if they catch it.)
No, Non immigrant visas don't require and exit ticket.
No catch, simular to if you enter with a tourist visa on the last day it's valid for, you still get 60 days. The Non-OA gives you 12 months everytime you enter on it, so if you enter on the last day it's valid for you get another year, so roughly 2 years without the need for an incountry extension.
Note however, everytime you enter the country you need to show 1 years worth of insurance otherwise you'll only be stamped in for the length you jabr valid OA insurance.
Outside Thailand you don't need to use the 14 Thai insurance companies. If you apply for an extension the insurance needs to be from the Thai companies, same with money in a bank.