I see where there is a "separate Teachers section available" with multi-year subscriptions.

Are there any other additional features with the multi-year subscriptions as opposed to monthly subscriptions?

Thanks in advance!

There are no extra features available for multi year subscribers. Monthly subscribers have the exact same features as any other subscribers.

I think what you're referring to is the Teacher Profiles feature that alumni sites have. We often refer to alumni sites here as "multi sites", but that designation simply means that their site includes Classmates from more than 1 graduating year. It has nothing to do with the amount of time somebody has paid for.