This is a long-standing issue. "Best move" means the best move after the book moves have been removed from consideration. The engine has Nc3, d4, c4, and Nf3 as book moves. c3 is not in its book, and is the fifth-best move as rated by the engine. So the first four are "book", and c3 is "best".
It leads to some funny evaluations, and 2. c3 is certainly one of those.
No idea about the second one, though.
I have noticed a couple of very weird things in game review recently. First of all, I was playing the Caro-Kann defense, and the move 2.c3 by my opponent was considered the "best move", which is clearly not true given that it is not a book move, and has only ever been played in 2 games in the explorer.
Second of all, on move 7, I apparently created a 'threat' to win a pawn. The threat text was highlighted, indicating that I should be able to click it and see what it thinks I am threatening, but nothing happens.