Tier 2 ILR set-O confusing questions

[amolpali]

Hi,
I am due to apply for my ILR soon. I have been on Tier 1 visa until 2017 and then switched to Tier 2 General Visa. I am bit confused about below question. What evidence I need to provide?
I got copy of CoS( electronic copy - not original). Is this enough or I need to provide documents like my employer posted advert in the jobsite and couldn't find suitable candidates etc(This is will be very difficult to arrange)?
Also do I need to share income proof at the time of applying for Tier 2 General last year? This is bit urgent so anyone who have processed ILR on Tier 2 General basis could give an advise please?

"For the period before you were granted leave as a Tier 2 migrant, documents showing that
you met the relevant requirements of the immigration rules."

Also this might be silly question but could you suggest what will be my Application date?
I have booked premium service appointment where I will take set-o form which is not yet filled in. The booking date outside qualifying period but the appointment date is within qualifying period so I hope Application date is the appointment date and not the premium service appointment booking date?