Pokemon-go – How to access settings in Pokémon Go when the top of the screen is unresponsive

I had the same Problem it's a Bug with the Gyroscope Driver in Cyanogenmod for the HTC One M8. Fix is not yet Released but you may try the Test-Version

Yes, there are critical hits.

The critical strike rate depends on the attack itself.

See here:

    Items {
      TemplateId: "V0022_MOVE_MEGAHORN"
      Move {
        UniqueId: V0022_MOVE_MEGAHORN
        AnimationId: 5
        Type: POKEMON_TYPE_BUG
        Power: 55
        AccuracyChance: 1
   >    CriticalChance: 0.05
        StaminaLossScalar: 0.12
        TrainerLevelMin: 1
        TrainerLevelMax: 100
        VfxName: "megahorn"
        DurationMs: 3200
        DamageWindowStartMs: 2400
        DamageWindowEndMs: 2700
        EnergyDelta: -100
      }
    }

Or here:

    Items {
      TemplateId: "V0032_MOVE_STONE_EDGE"
      Move {
        UniqueId: V0032_MOVE_STONE_EDGE
        AnimationId: 5
        Type: POKEMON_TYPE_ROCK
        Power: 55
        AccuracyChance: 1
   >    CriticalChance: 0.5
        StaminaLossScalar: 0.1
        TrainerLevelMin: 1
        TrainerLevelMax: 100
        VfxName: "stone_edge"
        DurationMs: 3100
        DamageWindowStartMs: 1400
        DamageWindowEndMs: 1800
        EnergyDelta: -100
      }
    }