Hi aps,
To answer your queries:
1. Yes you can apply 28 dates before your 5th anniversary date of entry. i.e., if you
entered on 3Jun2007, you can apply 28 days before 3Jun2012
2. UKBA states any continuos 12 calendar months in the 15 months prior to the application. So yes, you may show both a) and b)
3. Cohabitation - the recent two years before your application. Please read
http://www.immigrationboards.com/viewto ... ht=#537229
4. I personally believe UKBA will accept the letter from the council (seniors may have to confirm). However, if you can, it is better to also provide a Bank statement, tenancy agreement etc to support it
5. see above
6. see above
Good luck with your application.