Studies and ILR/Applying for ILR during notice period

[emABC1]

Appreciate any help on this as I haven't found anything yet to answer these questions.

I have been on a Tier 2 (General) visa with the same sponsor-employer (in England) since entering the UK. My entry clearance is dated September 1, 2016 and I entered the UK a few weeks later. On this basis I believe I'm eligible for ILR on September 1, 2021.

I have been offered a place on a master's course in England in my field of work to begin in fall 2020. The course is full-time only and it's quite an opportunity (in a non-crisis year I'm not sure I would have received an offer!), and I'm trying to figure out the immigration implications.

Scenario (1), start study in 2020: I understand that in order to undertake full-time study, I would lose my Tier 2 visa and switch to a Tier 4, and that the switch would erase the "continuity" I need for ILR, so that I'd effectively have to start the clock all over again after graduating in spring 2021. As a practical matter I think that means that I would need to be on a work or study visa until I could apply for ILR via the 10-year route. Is that right, or have I missed something? If I've had a Tier 2 visa for 4 years, after having a Tier 4 visa for a year, can I go back to Tier 2 (there is a 6-year limit on Tier 2, but does it restart if interrupted)?

Scenario (2), start study in 2021: Assuming I'd be admitted ... If I reapplied for the course to begin in late September 2021, would there a be a way to obtain ILR on September 1, 2021 then leave my job a few weeks later and go to school full time? I see that I'd need to apply for ILR with a letter from my employer with "confirmation that you are still required for the employment in question". Presumably they cannot give this if I've given them notice that I'm resigning to go back to school? What if not resigning, but taking a leave of absence? I can see that I take the risk of not obtaining ILR and not having a study visa either, and needing to withdraw from the course at the last minute and keep working.

Scenario (3), start study in 2022: I don't see any immigration issues with this, although the benefits to my career are much smaller if I wait this long to start the course.

Any thoughts are appreciated!

[zimba]

Scenario (1), start study in 2020: I understand that in order to undertake full-time study, I would lose my Tier 2 visa and switch to a Tier 4, and that the switch would erase the "continuity" I need for ILR, so that I'd effectively have to start the clock all over again after graduating in spring 2021. As a practical matter I think that means that I would need to be on a work or study visa until I could apply for ILR via the 10-year route. Is that right, or have I missed something? If I've had a Tier 2 visa for 4 years, after having a Tier 4 visa for a year, can I go back to Tier 2 (there is a 6-year limit on Tier 2, but does it restart if interrupted)?

You can switch back to Tier 2 or you need 10 years in total for ILR

Scenario (2), start study in 2021: Assuming I'd be admitted ... If I reapplied for the course to begin in late September 2021, would there a be a way to obtain ILR on September 1, 2021 then leave my job a few weeks later and go to school full time? I see that I'd need to apply for ILR with a letter from my employer with "confirmation that you are still required for the employment in question". Presumably they cannot give this if I've given them notice that I'm resigning to go back to school? What if not resigning, but taking a leave of absence? I can see that I take the risk of not obtaining ILR and not having a study visa either, and needing to withdraw from the course at the last minute and keep working.

Your employer must give you a letter that says they need you for the foreseeable future. You can resign after getting ILR but you may not be able to start your studies on time