Is what happened between the engaged couple, consisting of the defloration of the hymen without penetration, followed by full intercourse after the marriage contract and three days before the wedding, consideredzina (fornication) necessitating repentance and waiting for menstruation?

Applying for a marriage proposal does not permit seclusion with the fiancée, nor touching her, nor enjoying her. She remains a stranger until the legal marriage contract is concluded. The transgressions you mentioned before the contract are grave sins and a violation of Allah's limits, from which repentance is obligatory, as narrated by Abu Hurairah (may Allah be pleased with him): The Messenger of Allah (peace and blessings be upon him) said: "The son of Adam has his share of adultery decreed for him, and he will inevitably attain it. The adultery of the eyes is looking, the adultery of the ears is listening, the adultery of the tongue is speaking, the adultery of the hand is touching, the adultery of the foot is stepping (towards sin), and the heart desires and wishes, and the private parts confirm or deny that." (Agreed upon). However, these transgressions are not considered adultery (zina) and do not necessitate istibra (waiting period for purification), nor do they prevent your marriage, though repentance from them is obligatory. As for what happened after the legal marriage contract, there is no sin in it, for with the contract, the man owns the woman's intimacy, and she becomes his wife. It becomes permissible for him to seclude himself with her, see whatever he wishes from her, and engage in intercourse with her during permissible times.