it's possible because the immigration allows it. Even though around the world that is not how you are supposed to get a visa. You get a visa before you travel somewhere. That's the entire purpose of embassies. The fact that banks no longer give bank accounts for tourists makes it even less possible now than it used to be. And one day immigration may say "no more visa conversions, get a visa from the embassy like you're supposed to"
You should be getting the visa you need BEFORE you travel. Then the processing time is irrelevant because you are at home and planned for your travel. Then there is no need to worry about if converting to a different visa is possible. Or if one of the embassies around Thailand has a long processing time. Plan ahead and plan accordingly and none of that matters.
just because it's possible doesn't mean it's the correct way, and such should not be counted upon as it's not how things are supposed to be done. The ability could be stopped at any time.
1) You can apply for a 180 day extension on each entry. No one knows what this entails as we are still months away from the first extension even being possible. Or you can just leave and return and get a new 180 day stamp.
2) 90 day reporting is required. You would go to the immigration office at Chaeng Watthana to do your 90 day report since the first report is required in person, and the first report after returning from outside the country is required to be in person, so you might never be able to use the online system to do it.
No. The fact that the system is online changes nothing about the requirements. It just means you submit the application online. You still need to be in the country where you are applying through, and there's specifically a question on the application asking you to prove where you physically are located to ensure you meet that requirement.