Flag and putting - correct behavior on the green

Flag

According to golf etiquette, which players are the first to putt their balls on the green?
On or off the green, the player who is furthest away from the flag always putts first. It does not matter whether the ball is already on the green or not. If the ball is on the green, the flag must be served or removed from the hole. From outside the green, the flag can also get stuck in the hole when putting   . Of course, it must also be served or removed in this case. If another ball lies on the line of play, it must be marked by its owner. If the ball marker is still in the way, it can also be marked aside by the player.