Have you cleared it since you posted? From memory, I think I used the two other 'mon which match the ones in the grid and that helped do some dramatic clearing.
It's super-annoying that the F2P mechanic forces me to lose a heart even if I just want to look at the playfield to refresh my memory. I think F2P without an unlock option needs to die in a fire. An unlock option is the only way this game will get any money from me.
Yeah I cleared it on my 4th try (then caught it on my 5th).
I was annoyed because the 1st attempt was a total wash since I didn't know what I was getting into. Then the 2nd attempt I used a strategy that didn't work. 3rd attempt I used the right strategy but effed it up. 4th attempt finally worked. :lol