Hi,
The IOS upgrade/downgrade does not change the license feature set that you have currently install on your switch if you are reffering to the license, the only thing is the differences between the IOS versions that you will use.
For example if you are using an universal image this one contains all feature packages: LAN Base, IP Base, and Enterprise Services feature sets. The level of functionality available is determined by the license applied to the device. A software activation license (SAL) enables specific functionality. For example, an IP Base package license enables IP Base functionality in the Cisco IOS Software universal image.
Hope this helps.
