ILR Application Based on Tier 2- Previously on Tier 4

[sdsilver]

Application for ILR based on Tier 2.

My situation:
15 August 2014- Tier 4 Visa Approved
5 September 2014- Entered the UK on a Tier 4 student visa
25 September 2014- Started MA
25 November 2015- Tier 2 Application Submitted to UKVI
30 November 2015- Started work while visa application under progress as allowed
22 December 2015- Tier 2 Application Approved, states BRP valid until 25 November 2018
7 November 2018- Tier 2 Application Renewal Submitted
20 November 2018- In-person appointment for renewal and approval/issue date, states new BRP is valid until 10 December 2021

My questions:
1) I can apply for ILR after 5 years continuous residence under my tier 2 visa correct? Even though my visa is for 6 years total and does not expire until end of 2021.

2) On UKVI it states "your qualifying period can include time from the date your initial application (for entry clearance or leave to remain) was approved." From this wording I can apply 28 days before the 22 December 2020? Or is it 28 days before the submission of the original tier 2 application on 25 November? I only ask because I have found FOI requests where the Home Office has stated it's the date of application and others where they have stated it's the date the application was approved. I don't want to apply earlier than I am allowed but know the decision (without paying extra as I'm not sure work will in this case) can take up to 6 months so I would like to get it done at the earliest date.

Apologies for the confusing post. Normally I would just look at the entry clearance date (as most people probably do), however, I was already in the country when I switched to a Tier 2 so this doesn't apply to my situation.

Thanks!

[zimba]

1) yes
2) It is 28 days from completing the 5 years, counting from the initial Tier 2 visa issue/approval date