Is it explicitly mentioned somewhere that a child has to have ILE/ILR before applying for citizenship?

or this is a grey area ? (where I can try and it might work)...

The child was born before I became British citizen and before the mother got an ILR.

The child has a tier1 visa which expires soon.

Do I need to get an ILR for the child before filing mn1 ? (and registering him as BC)

My daughter was born outside the UK before I was settled, now I'm a British Citizen. She had a tier1 dependent visa but she left with her mom to the home country to stay there for about 1.5 years and come back. Her mom (my wife) is settled and has ILR. My Dougter's visa has expired while staying out...