Right now (as of the time I'm writing this) we don't have web API functions to create products and versions. You do that within the LimeLM interface. And thus right now there are a fixed known amount of products and versions in your LimeLM account (and thus can be stored in a datastructure you known and trust -- whether that is hardcoding or putting it in your backend database).
When we do add the ability to add products and versions via the LimeLM web API we'll also have the ability to query which products and versions are in your account: https://wyday.com/limelm/help/api/