Unreported sub depends on the rule set:
NCAA 8.3.3
Lots of things can be in play here, but basically if the offending team reports it before the offended team does, you simply officially enter the player into the game and all play up to that point stands. If the non-offending team reports it, then -well see the rule because a lot depends on the timing of the team's reporting it, offense vs defense, had the player made a play, etc.
NFHS: 3-6-7
The player is entered into the game and the HC is warned. If there is a subsequent infraction, the player is restricted to the dugout for the remainder of the game. The head coach is also restricted to the dugout for the remainder of the game.
USSSA: 5.5
1sst offense: Player is entered into the game, all play stands, team warning.
2nd offense: Player is entered into the game, all play stands, HC is ejected
USA 4.6C
Basically the same as NCAA
NCAA 8.3.3
Lots of things can be in play here, but basically if the offending team reports it before the offended team does, you simply officially enter the player into the game and all play up to that point stands. If the non-offending team reports it, then -well see the rule because a lot depends on the timing of the team's reporting it, offense vs defense, had the player made a play, etc.
NFHS: 3-6-7
The player is entered into the game and the HC is warned. If there is a subsequent infraction, the player is restricted to the dugout for the remainder of the game. The head coach is also restricted to the dugout for the remainder of the game.
USSSA: 5.5
1sst offense: Player is entered into the game, all play stands, team warning.
2nd offense: Player is entered into the game, all play stands, HC is ejected
USA 4.6C
Basically the same as NCAA