So activated my new 6. When I go to app store, it is asking for password to an old apple ID I haven't used in years. iCloud, iTunes match, etc all are associated with current apple id.
Sounds rather odd. But try going into Settings -> iTunes & App Store and signing out of whatever account is there by touching on the Apple iD at the top of the screen and choosing Sign Out. Then log back in with your current details.
Do you have old apps trying to download to your phone that were from your old Apple ID? If so, it will ask for your password to your old Apple ID so that you'll be able to download those apps to your phone.
Do you have old apps trying to download to your phone that were from your old Apple ID? If so, it will ask for your password to your old Apple ID so that you'll be able to download those apps to your phone.
Just to add a note, it's not like the App Store will put old versions of apps on your phone, the apps will be the latest version of the app. In case anyone is confused.