"multiple versions" is more or less just 2.0 and 2.1 at the moment, but plugins should be able to specify that they support multiple versions in the same way they say it for a specific version

if needed: a way to make this backward compatible is have the old version as the first comment, then allow the next one to be what specifies the other version(s)

edit:
alternate methods

• add this to the 2.0.6 minor release and not try to actually be backwards compatible
• instead of specifying with multiple comments, have a range
• use semver
• make plugins check manually, with mod version as a failsafe