Collections is not worth the trouble. If it can be removed randomly without notice by the dev, then it is pointless to bother with it. Many games being given away for a limited time have a 'claim' button but the dev doing the giveaway has to enable that functionality on their end. My suggestion was that the default be 'always claimable' so that devs don't need users poking them about it to enable a functionality they may not be aware was there at all.
Here is an example of a limited-time free giveaway with a claimable game:
