Google App Engine version numbers?

Question

How do App Engine version numbers work? Are they only integers? Can I use floats? Can I reuse old version numbers?

Answer 1

You can increment it when you pushing a new release. See below for reference.

When you build a new major release of an application that is already running on App Engine, you can upload the new release as a new version. The old version will continue to serve users until you switch to the new version. You can test the new version on App Engine while the old version is still running.

Edited: Didn't remove my answer because there're some good comments on it.