recommended best move
Depending on search depth, the engine comes up with different moves. The higher the depth, the better the move, generally. Since you're a free member, the search depth you have access to is limited.
My bad, I didn't check your profile. And yes, the longer the engine thinks about a position, the more things it sees, that's why the evaluation is likely to change over time causing the program to consider a different move as the best.
alternative move that works just as well.