How long will it take for apple to reset my upgrade when I return my iphone 5

I'm sorry, but Apple does not provide a downgrade path for iOS. Because downgrading is unsupported by Apple we cannot discuss it on these forums, but you can use Google to find information on how to install an older version of iOS on an iDevice.

Apple doesn't reset your upgrade because Apple has nothing to do with this.

Contact your carrier and ask them... it's their system that must reset the upgrade.