An A7 key also unlocks A6. I know that because I had to revive an old A6 project from mine.

A6 projects will run under A7 anyway. Only my problem was that I had some A4 keywords in my old A6 project, like REMOVE instead of ent_remove. That did not work with A7, in fact it also did not work with A6.60, I had to use A6.40.