PBS Tier 2 Dependant Visa extension 2 months short of ILR qualification period

Hello Moderators,

I'm hoping you could guide me on what to do per my situation below. I'm newly registered to this site and quite grateful for the wealth of advice, information and help you've provided to people over the years. It's simply amazing. I've searched for and read several situations before registering and forgive me if this has been answered somewhere of recent then feel free to link me to it as I haven't being able to see a similar circumstance to mine in a sense and just looking for some clarity.

I hold a PBS Tier 2 Dependant visa. Entered the UK 13th Dec, 2016.

Entry Clearance Visa validity was: 12th Dec, 2016 to 11th Jan, 2017 (one month validity)
First BRP issued on entry, validity was: 28th Nov, 2016 to 13th Sept, 2018
Current BRP expires by 1st Sept, 2021

Regarding the 5 years stay requirement for ILR and the 28 days prior which makes one qualified to apply for ILR, my confusion is this:

1.) Which does my 5 years count from, the date on my entry clearance visa or the date on my first BRP?

2.) How does varying an application work if it does happen that I'm 2 months short of the ILR 28 days qualifying period? And is there a chance of it being applicable to my circumstance based on your answer to my question above?

Thanks in advance for your help.

1. BRP date in your case
2. If you apply for a new application while another is pending, the new application will be considered a variation. You should apply for an extension under the dependant of skilled worker and vary it to ILR later using a new SET(O) application.