Query on ILR Application Date and Absence from UK

[tapp00]

Hi

I am due for ILR this year and trying to find out few details on earliest dates and what documents are needed. My employer has mentioned they don't support ILR applications so will have to work things out on my own.
I have been with the same employer & my Case Details as follow:

Date of Application: 30th July 2021
Date of Biometric: 9th Aug 2021
Visa Approved: 10th Aug 2021
BRP Issue Date: 10th Aug 2021
Employment Start Date: 23rd Aug 2021

It was an in country switch from Tier 2 ICT (came in 2020) to Skilled Worked Visa. I was in the UK during my skilled worked visa process, so there is no entry clearance date for me.

What is the earliest I can consider to apply for ILR?

Also during my tenure on Skilled Worker I have taken absence from the UK based on my manager's approval but never more than 180 days & have worked as well during my absence period for no more than 2 weeks.

Now the problem is my manager was based out of another country and he was aware of my absence but he has now left the org, and now I have a new line manager who is not aware of any of the details about my absence and my work agreement with my previous manager.
For ILR application does the employer or the manager needs to provide my absence details on a company letterhead or i can provide that as a document itself?

[zimba]

Read--> All you need to know about the sponsor letter for Skilled Worker route

Also read --> All you need to know about applying early, the application date, 28-day concession and more

[tapp00]

Thanks zimba for your response, so i can actually count from Date of Application - 28 days?

I was actually serving my notice period with my previous employer during that time, does it matter at all or is it safe to go for Date of Biometric - 28 days?