You were allowed to move to the green spot because the rook wasn't promoted yet, it would only be after it moves again. Otherwise, dropping would be too powerful. See the drop rules:
... nor does dropping within the promotion zone result in immediate promotion. Capture and/or promotion may occur normally, however, on subsequent moves of the piece.
Shogi Notation notes which piece is moving, and where they are moving to. So P7f means that a Pawn is moving to square 7f. If there is ambiguity as to which piece is moving then the starting location is added to the front (ex. G6i-5h when there is more than one Gold piece that can move to the 5h square)