different offices may have procedural differences concerning documentation and that kind of thing but not in this case. This is the fundamental concept of visas working at a national level. It is enshrined in immigration law, so no, different offices cannot do this differently.
I don't think so. This is normal practice. I've never heard of having to restart a visa just because you change your address to a different province. All you have to to is go to immigration and register your new address.
I moved to a different province halfway through my retirement extension period and there was no disruption. It just continued until the expiry/renewal date.
yes let's not pretend. I have my sources. But I also have my personal experience when I used the services of an immigration officer once in Phuket many years ago. For a fee he would take your passport and drive to Sadao and get a stamp in your passport while you lie on the beach. Not long afterwards he got busted while being in the possession of seven passports whose holders were deported. Yes I'm sure that this scheme is going to work most of the time, it's just that in Thailand you never know what crackdown is coming and I've seen a few in the 27 years I've lived here including in the company registration and property sectors. But good luck anyway.
that's correct, using an agent isn't illegal if what they do is legal. I've lost count over the years of how many immigration officers have been busted by the Bangkok bosses.