visa application details and questions (Tier 5)

I am currently on a different visa category (Tier 1) but will not be able to renew it so I am going home to apply for the Tier 5 Youth mobility visa scheme.

i have 4 questions:

1. My current visa will expire soon (15 Jan 2011) but just so I get a headstart, I went and paid for the application fee for the Tier 5 visa a few months in advance ... so I might get the Tier 5 visa start date to be in December 2010.

Is this permitted, having two visas for a short period of time? Just wondering if that would get my application rejected.

2. I know that officially the Tier 5 Youth visa allows anyone from the list of countries approved to apply as long as you fulfill the age/citizenship and funds, and if you have never been on a Tier 5 visa before. Question is, if you have been on visas of other Tiers (like Tier 1) would that be a disadvantage to applying for Tier 5 Youth? Or does it not matter (though it looks a bit stupid that I would go from a normal working visa to a temporary work visa ... but it's becase they changed so many rules the past year!)

Two other questions, really dumb:

3. In the application, it says for documentaion of personal details: 'UNLESS SINGLE, please provide evidence of your marital status ie marriage or civil partnership certificate' but my status is listed as "unmarried partner", so do I need to provide evidence of "unmarried partnership"? If so, with what?!?!

4. If quoting reference numbers for UK student visas - do you quote the VAF no (in black) or the red number at the top of the page? So many conflicting answers in forums ... so if anyone has official knowledge, please do share!

Thank you very much