A few ILR queries

[jonno22]

Hello.
In a few months my wife and I will be applying for my wife’s and my stepson’s settlement (ILR) as they will both have been living with me in the UK here for exactly five years as of 06/06/19. I am a British citizen.
I have a few questions, that I would really appreciate answers to:

1) Will my stepson require a separate online application form? I suspect (and hope) not as he is a dependant of my wife’s. He will be 16 years old at the time of the application.
2) As already mentioned, my wife and stepson will have here for 5 years as of 06/06/2019. Their current BRPs expire on 10/09/2019. Am I correct in assuming that we can make our application anytime between 28 days prior to 06/06/2019 and 10/09/2019?
3) How do we know which supporting documents we need to prepare for the UKVAS visit? I assume that they will in the most part be the same as those used for the FLR application, with the addition of a new English language certificate and the life in the UK test. We certainly have most of them (marriage cert, my wife’s previous divorce cert etc.), but we don’t want any nasty surprises as most of my wife’s documents originated in Ukraine, so getting extra ones would take time. For example, for my wife’s FLR application a couple of years ago we also needed a notarised letter from my stepson’s father stating that he was happy with my stepson (his son) remaining in the UK. We only had one of those, so we would need to get another one arranged if required.
4) For the FLR application we had to make two photocopies of all our supporting documents. Is this required for the online ILR application as well?

Many thanks in advance.

Jonno22