Tier 4 to Tier 2 CoS/Visa start & end date

[T4toT2]

My First Tier 4 visa issue date- 22/03/2011
My first day at UK (Departure)- 30/03/2011
My current Tier 4 visa expires on- 30/01/2018
Will be eligible for 10 years route after- 03/03/2021

So the game plan is if i get my tier 2 visa up to 03/03/2021 i will be eligible for ten years route. To achieve that can these following be done (assuming they will give 14 extra day with the CoS/visa end date as per previous so many records)-

Scenario-1: Full flash ten years (if below step is legal to follow)

Cos Issue date- 20/12/2017
CoS work start date- 03/03/2018
CoS work end date- 03/03/2021
Visa application date- 28/01/2017
Visa End date- 17/03/2021

Scenario-2: 20 days short from 10 years route (excluding 28 days grace period)

CoS Issue date- 20/12/2017
CoS work start date- 29/01/2018
CoS work end date- 29/01/2021
Visa application date- 28/01/2017
Visa End date- 12/02/2021

Many Thanks in advance for your time and effort to respond on this regards.