HSMP 2006 Issue

Hi ! can anyone help me in this please !

1- I applied for the HSMP before April 2006 (but my approval letter was dated May 2006) ,
2 - I got EC visa stamped on July 06 and i entered in UK Sep 2006,
3 - then i applied for FLR (under new rules) after 8 months in July 2007 and
4 - I was granted further 4 years extension that is valid till July 2011.( 1+4 year case)


My questions are:
- My initial hsmp approval letter is dated may 2006 ,how would they know that my application was sent before April 2006?

- If i am eligible Can i Apply a year before my visa validity expires

Kindly, let me know i am not cleared in any point of my case.

Thanks