"How can I replace Cisco T Series IOS to a diff series?"
The T train becomes the next mainline train. So if you were running 12.3T, 12.4 would be the upgrade path for all the features that the 12.3T concluded with.
"What are feature set of Cisco T Series IOS?"
That varies. T trains are works-in-progress. Newer versions within the same T train support new hardware and/or new IOS features. New features are documented as released. They are also sometimes described before released, and what release they are expected in.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...