My theory is that the System behind FKG is similar to the RNG in Pokemon. In Pokemon you can manipulate the RNG (called RNG Reporter) simply by log in at a specific time and raise your Frames before you can catch your Pokemon with perfect IVs and the Nature you want.
I think in FKG you can raise your Frames with the three 3* in a row or one 4* Normal Gacha Trick and after that you participate at a specific time in the Premium or Limited Gacha to get a 6*