Not quite sure if I understood your question, but if you're asking for commercial subscription support, you should consider redHat's EAP here: https://access.redhat.com/site/articles/112673
You can see that EAP has a life-cycle of its own, and picks JBoss products and versions over certain others.
When it comes to differences I guess the topic is quite vast: starting that different versions comply to different JEE versions - that would be quite a feature difference!
If you start with your development I would use the latest available version (i.e. EAP6.1.Beta which is a AS7.2 community version)
Here you will have the full EE6 functionality. And it makes no sense to start with an old version.
For older (EJB2) applications it might be an option to use AS4.2, 4.3 or 5.1. But you should keep in mind that you will not be able to have patches except you pay for a Red Hat subscription (as Pasquale mentioned).
With such EJB2 application you might loose features as starting with AS7 (EE6) EJB2 is an old standard and will be EOL as with AS8 the EJB2 Entity support is removed as with EE7 this is pruned and optional.