No, there are 90 day ED visas that require you to go every 90 days and apply for an extension (like the STV) and there are 1 year ED visas that require you to do 90 day reports.
There are 1 year ED visas. All university based education programs issue 1 year ED visas. As a rule,, language and muy Thai schools only issue 90 day ED visas,, but all 3 people I've seen have 1 year ED visas.
It's the same as a volunteer visa. You can legitimately go to school, or you can find an agent that sells ED visas.
B) Only language programs, and only if you're doing them legitimately. Plenty of people come to Thailand and study 2-4 years at universities, or find agents and just buy ED visas.