If you are going to buy and sell bitcoins then you need to comply with the requirements of the state and you must have a business permits. If you will not comply your business cannot operate or will be disallowed by banks to do further transactions. And so to be sure that the government and banks will support your business you must abide by the law.

If your country has not declared bitcoins as illegal, you CANNOT buy or sell bitcoins. Only companies/exchange websites need to have a license to operate their services and NOT individuals.

Bitcoins is not yet banned in most countries but when you deal with bitcoins, you need to make sure the company/individual you are dealing with is trusted else you can be questioned about its source or those funds will be frozen for investigation.

It would really be country-specific so it's hard to give you a definite answer. Probably the best way to recognize whether you'll need additional requirement would be how tightly they regulate bitcoin in your country. In my country for example it's possible to just make a wallet and buy and sell bitcoins face-to-face and the government wouldn't be any wiser.

If you'd want to do it without risking meeting up with strangers though, you'll have to go through exchanges which are quite strict with identification. I made an account before our government released a circular requiring exchanges to register as money transfer companies. Even without the government breathing down their neck, they asked for addresses, a selfie and a photo of a government ID and it took days to complete my registration.