I have a doubt about the notations of writing down moves. Also, all these examples are from real games in the database so I don't think the players were analyzing by trying out different moves etc. I would like to understand what these symbols indicate.
Q1: Consider these moves:
1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.g3 Bb4+. What does the + sign at the end of
Q2: In the following moves
17.Nxg6 Rf7 ( hxg6 18.Qxg6+ Kh8 19.Qh7#) 18.Nxe7+ Qxe7 there is something written inside brackets which seems to indicate move 18 and 19. Also there is a hash sign inside the bracket. But after the bracket is closed, we have move 18 again. What does this indicate?
Q3: In the following example, there is a dollar sign after move 6:
6.Bc4 Be7 $2 7.Qb3 Na5 8.Bxf7+ Kf8. What does these indicate?