Rule_follower

A situation occurred in our 12U tournament (Championship game no less) this past weekend and would like insight on the rules and proper handling of the occurrence. It was a bit muddy as to if it was an illegal substitution or batting out of order so please bear with me. Background: Tournament rules state that you have to bat your entire roster/team. Umpires are high school kids and not professionals so vast experience and knowledge of all rules/situations not expected. Situation: The lineup card provided by the opposing team to us and the umpire had 11 kids listed; however, their book and posted batting order had him on there (realizing that both of those are unofficial and didn't align with the official lineup provided to umpire). In the 2nd inning it was noticed that the batting order was off by 1 (ex, B7 was B8 jersey number and the on deck batter B8 was B9s jersey number). We thought that B7 and B8 were batting out of order so when B7 got on base we called time and alerted the umpire. The opposing team coach said the order was correct, but when should him and the umpire the lineup cards provided the coach saw that he didn't have his 12th player #34 listed in the lineup and he batted in the 4th spot. There was much discussion as to how to handle the situation. In the end it was agreed that because the tournament rules require you to bat your entire roster, #34 would be added to the lineup in his initial batting spot of the 1st inning (4th spot), an out was assessed to the opposing team and the game proceeded. It wasn't a normal situation and other factors forced an agreed to and quick decision so as to not waste time and keep the game going. What is the proper way to handle this? 1) Is #34 considered an illegal substitution since he wasn't listed on the lineup card? Is #34 even eligible to play since he wasn't listed? 2) Since the missed player wasn't caught until later is there even a penalty since he established himself as a legitimate batter during the 1st inning (which you wouldn't know until after the fact or allowing additional innings to be played while you tired to find the mistake)? 3) In general do you have to catch batting out of order the first time it occurs or whenever it is first noticed (assuming they continue to bat out of order next time through lineup)? 4) Opposing team stated that providing a lineup card is a courtesy and not a requirement. Is that true? How does that make sense since you wouldn't know anything related to batting order, substitutions, player ID or how many players? Appreciate the time and feedback.