Freeze is only status effect that relies solely on being activated through secondary effects of moves. This makes the freeze condition a rare occurence.
The weather condition Strong Sunlight can prevent freeze from occuring when active but will not cure freeze after it has been inflicted.
Before the frozen Pokémon attacks it has a 25% chance to thaw. This includes the first turn it is frozen, so, if it is frozen before attacking, it is possible it will thaw even that turn.
Most Fire type moves have the ability to end the freeze status effect. In addition the moves Flame Wheel and Sacred Fire can still be used by a frozen Pokémon and will thaw it.
The Aspear berry will cure freeze as well as the cure-all berry the Lum berry.
The ability Hydration can remove the freeze status when the weather is Heavy Rain.
The moves Aromatherapy or Heal Bell will cure this status for everyone on the team. Safeguard can prevent this status affect from being inflicted on a teammate.