How long are the halves
Check with the coaches. They know to the second how much injury time should be played and will know how long the halves are. I thought in England they are pretty standard. But check with your RDO he should know or the secretaries of the youth leagues you officiate in.
That's risky. Yes, they should do, but they don't always.
No referee should ever be going into the game not knowing the exact rules for that competition.