In super challenges in order to increase your chance to win like others You can either buy the full heart pack or invite a friend of you who joins an upcoming supper challenge. As the invited person joins an upcoming supper challenge both of you become full heart. To do that you need first of all complete your profile. For the persons who have not completed their profiles, invitations will not work and they will not receive any full heart pack.
there is no limitation for the number of your invitations.