Welcome to the LM community, canuckinjapan!
Well, if your instructor can purchase some of the older releases, either from this website or at a quarterly instructor gathering, then YES, he could learn and teach some of the older realeases. (However, sometimes older releases are hard to find and purchase.)
For example, before we launched Body Jam 44, I was mixing a little of 37 and 39 into my classes to keep things interesting/fresh before the new launch.
Sometimes, when Les Mills "twees" or makes changes to the format of a program (as is what happened to Body Jam around release 32 or so) they will ask that instructors only go back so far when mixing.
So, to answer your question- IF your instructor can find and purchase some older releases, than yes, you can go back and learn them.
Good luck!
cbc