Tier-2 ILR absence and dependent visa clarification

[GKJ5]

Hi,
Firstly, I would like to thank for the forum supporters, this is really a useful forum and its almost a guidance for my ILR. Really appreciated. And I hope I will get answer for my questions.

I am a Tier-2 Skill Migrant, I entered to the UK as a Tier-4 student and I had an yearlong industrial placement outside the UK during my studies (I understand Tier-4 period will not be counted to ILR). After my graduation, I switched to Tier-2 (General) and my wife entered to UK two years before as my dependent. Now we both having visa till 2019.
I have completed five years in Tier-2 permit, now I am planning apply for Indefinite Leave to Remain (ILR) sooner.

However, according to UKBA rules, my wife needs to complete five years of stay in the UK to apply as a ILR Dependent (Please correct if I am wrong).

My questions are.

Q1. Can my wife be in the UK with the same permit till end of 2019, even if my visa category has changed to ILR? And what will be the next visa permit from September 2019 to January 2021.

Q2. I was in the middle of filling SET (O) application and can I consider my Tier-4 Placement as ‘absence from the UK’ or ‘previously lived in a country outside the UK’ or I need to mention in both areas?

Q3. Any further supporting documents apart from following:

1. SET(O) filled and signed
2. Appointment letter with booking/Payment confirmation
3. 2 x Passport size photos
4. Passport
5. BRP
6. Life in the UK test PASS notification letter
7. Degree Certificate
8. Confirmed English language requirement
9. 1 Recent Month Payslip (Computer generated)
10. 1 Recent Month Bank Statements of Salary account (Received from bank with seal)
11. Employment letter from current Employer ( Standard Occupational Classification (SOC), Salary, Working hours, Required for foreseeable future, Absences included)
12. Letter from Previous Employer confirming Absences

Thank you.