good behavior
Something you only need to maintain while you're in da slammer --- once you get released again, anything goes.
Once you get your imprisonment-sentence shortened considerably for good behavior, you can return to the street and then be just as bad as you please until you get busted again.
good boi behavior
Being well-behaved, respectful, and courteous, and willing to compromise.
She has such good boi behavior because she always studies and compromises on her boundaries with others.