my Spouse Visa extension

Hello,
I have few questions regarding my wife visa.
I am on a 5 years Tier 2 (General) visa from 20/02/2015 to 20/03/2020.
My wife came as PBS Dependent from Iran with visa validity from 12/11/2017 to 20/03/2020.

In January 2020 (28 days before expiry of my visa), I am going to apply for ILR through the priority service.

I have following questions:

After I get my ILR, do I need also to apply for my wife for extension (before expiry of her visa)? If so what category would her visa extension be? Would it be a PBS Dependent or ILR Dependent?

What I should do to make sure her current stay as spouse in UK is not vanished and she can apply for ILR after completion of her 5 years stay?
Thanks
Ali

She applies for a 3 year PBS dependent extension before her current visa expires if you hold ilr and she meets the requirement and maintenance funds.