Depends which embassy/consulate you are applying with. Some require 1 month, some are 3, some are 6. Best to be specific about location in your question.
Once it is granted, it is valid for 5 years. You can receive the visa now and wait 4 years before using it for the first time if you want. It is "activated" as soon as the visa is granted.
I can answer your first question. You get a 180 day stamp upon entry, then you can either choose to extend for another 180 days at an immigration office in Thailand, or exit the country and re-enter for another 180 day stamp.
If it's an evisa application then they will email the visa in a PDF when approved. Print the visa and present it at immigration when you arrive at the airport in Thailand. They will then stamp your passport with a 180 days entry stamp.
Anonymous participant nope, at first I submitted a brokerage statement of my investments, but they then asked for a bank statement showing I had 19k cad in chequing or savings. They didn't mention anything about how many months were adequate.