U21 substitutions

[SSS]

It's in another thread, but may be lost there -
Four subs were used by the U21's on Saturday.
Can anyone confirm that this is acceptable in the U21 competition?

[Cityace]

It wasnt a league match, it was a cup match so there probably allowed.
Not certain though,if it wasnt allowed i'd say someone would have kicked up a fuss already,since almost everyone at the game noticed it.