That's a forthcoming tournament with presumably a different qualifying date of birth for participants. If you go on to the FA's website you will see that he was playing for the England Under 18s against France a few days ago.
Whatever the rights and wrongs of the selection decision no club or manager can be expected to tolerate agents attempting to influence team selections.
Yet despite an outstanding goalscoring record for us Byrom never played in the top flight again after the age of 22 in 1966. Why was that ?
Injury, attitude ,opponents rumbling a weakness in his game, switch of tactics in the game to 4-3-3 ?
Denis Law once scored six goals for Manchester City in an FA Cup match against Luton which was abandoned with City leading 6-2 after 69 minutes. The match was replayed and City lost.
None of the clubs you refer to had their issues from being in the Premier League - which is the most popular football league in the world - so I have no idea why you have dragged them in to it. The FA don't have sufficient jurisdiction - it is the EFL who have the jurisdiction. The new system for the independent regulator provides for more protection for clubs from unsatisfactory owners.
In the case of young players who interest Premier League clubs like Arsenal no Championship club is going to be able to match wages available from the Premier League club. The question will be whether the player - more likely his family - thinks it is in his long term interests to stay at the Championship club for the time being.