ILR for spouse query

[Bestcoffeelondon]

I got my ILR via the 5 year route (was initially on a work permit and the last portion of the 5 years was on a tier
2). My spouse then got the leave to remain initially
for 2 1/2 years and then leave to remain again for another 2 1/2 years which ends on 20th October 2017.
A) Can my spouse apply for ILR from 28 days before the 20th of October? B) Does the application need to be made latest by 20th October? C) my research tells me that SET (M) is the right form to use - is this correct?

Thanks!