No that visa only allows you to “stay” for 90 days. When you get your first year extension they’ll usually put a slip of paper in your passport to inform you of when your first 90 day report is due.
Generally the first one must be done in person and then you can use the online system.
Whether you’re talking about an actual visa on arrival (that you physically pay 2,000 baht for) or a free visa exempt entry - which many confuse between the two there is no set limit. It’s at the discretion of the immigration officer.
He doesn’t need to extend it yet. He’s only just arrived. Even then they probably won’t extend it anyway if the expected fee of 10,000 baht plays out (we don’t know yet). They’re better off to do a border bounce for cheaper.
Not sure what you mean here. The OP just landed and got a 180 day stamp on arrival. Irrelevant what month they got it. It couldn’t have been before July 15th.