Visa extension (skilled worker) with expired EU passport?

Hello everyone. I was wondering if anyone had a similar situation.

We are a family currently residing in the UK on a Skilled Woker visa using a European passport. We are due to extend our visas soon. Unfortunately, my son's passport expired and it will not be renewed soon.

My questions are:
1- Will it be possible to extend my son's visa using his expired EU passport through the "UK Immigration: ID Check" app, similar to what we did last year, even if the passport has expired?

2- We all hold a dual citizenship, the second passport is a non-EU passport. If the expired EU passport cannot be used, can we use my son's second passport for the ID check, while the rest of the family continue using the EU passport? Would that be done through booking an appointment at a UKVCAS Service Point?

I called the home office enquiries number and unfortunately they were unable to answer these questions.

Any guidance will be more than welcome!

Following this subect, I called the home office and the agent suggested to put 0000000 for the passport number and a future date for expiry date as using an expired passport won't let me go through, and then add a cover letter explaining the situation in the end.
As a test I tried creating a new child dependant skilled worker application, and once I tried to scan the passport using the UK immigration app, it rejected it saying the document is expired.

I think I will eventually require using the BRP appointment route for IF verification. If we do that, whether using the expired EU or the valid non-EU passport, would that affect the counting towards ILR? Does the whole period have to be on the same passport to be valid towards ILR?

Thanks

The ID app will not validate an expired passport as you have found out.

Qualifying period does not have to be contained or covered by 1 passport.