New subscription..2011

I am currently running the latest version of norton internet security, that is due to expire very soon..

I have an unused 2011 internet security 1 year 3 pcs subscription that i want to use up.

Will i be able to add this at the end of my current subscription?

Will it stay updated to the current version?

Will i have to uninstall my current version first to be able to use the 2011 version?