I have got an offer from a company in germany and I am applying for the work visa.

I have a few questions that i need to sort out.

Work Contract:
My contract states that the start date is Oct 1st and I got the appointment for 24th Sept. Will that be a problem?
Also the company signed and sent me a scanned copy via email. Will it work or do I have to get it via courier?

Proof of qualification: I did my BE in computer engineering from Mumbai university. Do I need to get the degree evaluated by ZAB or just the xerox of the degree is fine.

Experience certificate from my current employer:
I currently work remotely (from home) full-time for a company in UAE. Do I just submit the experience letter from that company or do I need to attach payslips. This also is in signed scanned format.

What is Federal Employment Agency approval:
Do I need to get that before going for the interview?

Did you buy your departure ticket and travel insurance before going to the interview and submitted to them? 
I believe we have to submit the travel insurance and ticket to them, so what date should it be?

Thanks.

 Hope to get a quick response.