Every hand is an opening
Heads-up, the button IS the small blind: you post 10 into a 30-chip pot and get to raise for cheap. The default is to open-raise the large majority of hands — min-raise keeps the price of stealing tiny and leaves the most room to fold to a three-bet; a 3x open builds bigger pots for your value hands. Trash still opens: if the big blind folds even a third of the time, any two cards print. Only against a big blind that defends wide AND three-bets hard do you trim the bottom of your range.