O to B for life, then to B's eldest son for life, then to C and his heirs, but if liquor is ever sold on the premises during B's or C's lifetime, then to X and his heirs. B and C are both lives in being. This interest satisfies the rule. To A and the heirs of her body, then to the daughters of C then living and their heirs. The interest in the daughters fails.
Ages are irrelevant.
To A for life, then to the daughters of C then living and their heirs. This does satisfy the rule. This is a contingent remainder because we don't know whether any of the daughters will still be living when A dies. Surviving A is a condition precedent making the remainder contingent. O to B for life, then to B's eldest son for life, then to C and his heirs, but if liquor is ever sold on the premises during B's or C's lifetime, then to X and his heirs.