MintyDisciple

Not a researcher or anything, and I don't have any access to the save file, but I would like to say that the rules of the Singapore Premier League (and the Singapore Cup) are such that teams in the league are required to field 2 U23 (not U21) players in the starting 11, and if these players have to be substituted in the first half, they can only be replaced with other U23 players. In the second half, these 2 U23 players can actually be replaced by senior players. This is how it's supposed to work. The league regulations can be found here: http://s3-ap-southeast-1.amazonaws.com/fas-org-sg/

The Young Lions cannot qualify for continental competitions due to the fact they exist primarily to develop the young players in the country, meanwhile Niigata Unicorn (Singapore) and DPMM are foreign teams in the league and so they won't qualify for continental competitions as well. You might have to change clubs to play continentally...