It's possible that Lapras may have been Solidad's starter pokémon, because according to Drew, Lapras has been with her for a very long time. Lapras debuted in the first round of the Kanto Grand Festival where it used Sheer Cold to freeze all the water in the pool. Its magnificent performance earned Solidad second place in the next stage.
Lapras was next seen in the Top 16 battle where it froze its opponents and then Solidad's Slowbro blasted them with Hyper Beam knocking them out. It was last seen in the Quarter-Finals where it was used alongside Butterfree.
+ indicates this Pokémon used this move recently.* - indicates this Pokémon normally can't use this move.
It's actually unknown which Pokémon froze Girafarig and Zangoose since only the last part of the battle was shown.
Slowbro, who was fighting alongside Lapras at the time, is capable of learning Ice Beam but Solidad's Slowbro has never actually been shown using Ice Beam. Since Lapras is also an ice-type, most assume that Lapras was the one who froze Girafarig and Zangoose.
Additionally, Solidad's Slowbro was already capable of using four moves, although it should be noted that some Pokémon have been shown using more than four moves in a single episode in the anime.