Every amphur has different rules and regulations for yellow book and pink ID card. At some it's a simple process, at others it's very complicated and takes lots of paperwork, witnesses, and many months. Some will refuse to do it flat out. You have no recourse except follow the process of your amphur.
2) you need to at least put flight information. Find a flight and put the information. Some embassies may require an actual booking
3) depends on the embassy
4) you cannot arrive on August 14th and apply for extension. You can only apply for extension when you have 30-45 days left on your entry stamp. You can apply for a single re-entry permit and then apply for the extension when you get back.
what's your point? This person said they would get a non-O and then get the marriage visa. I corrected them telling them that the non-O IS the marriage visa. Your post doesn't change or add anything to that
they can't force you not to leave. But if you do and they find out, they will cancel your application with no refund. You must remain in the jurisdiction of the embassy you apply at the entire time until the visa is issued.
That is not something you should count on anymore. That used to be possible before Covid, but not since. They started cracking down years ago, and since they changed visa exempt to 60 days they've been VERY strict. Many people who have entered and gotten a 30-day extension then left have been pulled out of line at the airport and interrogated after only their 2nd entry, and told to get a long-term visa or be denied entry next time.
Just because there is no rule does not mean it's unlimited.