A basic principle of hoops says if a player gets to a spot first, they are entitled to that spot (few exceptions, e.g. other player already in the air on a try).
Situation 1: L is in A position in frontcourt, A1 has ball in L’s corner with no defender. A1 drives to hoop, B2 is standing still (never moved) at lane, A1 brushes off side of B2. RULING: Play on, B2 entitled to that spot.
Scenarion 2: B2 standing in lane with back to A1 (perhaps B2 is defending A2), B2 never attempts LGP as they have back turned, but they are entitled to their spot. A1 drives to hoop and either (a) brushes off B2 with no displacement, or (b) displaces B2. RULING: (a) no call; (b) player control foul