At the opening kickoff, if a player enters the opposing side to kick the ball backward, is this legal?

At an opening kickoff, it is indeed legal for a player to enter the opposing side and kick the ball backward. The Laws of the Game, specifically rule regarding kickoffs, allow players to take the kickoff in a direction they choose, as long as the ball is moved forward into the opponent's half of the field. The intention of this rule is to create an opportunity for creativity and strategy in the kickoff procedure, enabling teams to devise various formations and plays.

Additionally, it is important to note that there aren't specific restrictions on the direction from which the ball is played during the kickoff, as long as it is done fairly and in accordance with the rules. Therefore, the act of kicking the ball backward is totally valid and within the rules of play, promoting tactical diversity during the game.