Turnover limit of a unregistered trader and accounting.

1,what is limit of turnover of an unregistered trader.
2 can an unregistered trader purchase goods from an unregistered trader .
3,can he purchase goods from interstate from a registered or unregistered trader .
4,can he sale goods in state and other state to a registered or unregistered trader .
5,is he is liable to keep sale purchase voucher and accounts for showing purchase sale turnover?
6,what will be done when any assessing authority comes his business and ask for registration.