Reserves team problem

[chapi9999]

My b team (Real madrid) 

I can't make the second team lineups and the coach destroys the lineups by putting players in different positions and prioritizing bad players over good ones.

On the other hand in the national teams: If I select one player for the first team he shouldn't be eligible for the under 21 team. many times they play with the under 21 the day before

[passenger58]

From my experience you can't influence reserve team lineups, but the issue where players are picked out of position is a long running one which has been reported, I believe. 

[TheHurricane]

You can influence the tactics that are used for your reserve team but not which players are used.

I believe the issue with players playing under 21 internationals at the same time as they are in the senior squad is a known issue that SI are investigating.