Is it permissible for the suitor, after the marriage contract (aqd al-qiran), to visit his fiancée and be alone with her in her family's home and engage in certain acts? And is this considered consummation (dukhool) if the contract is annulled? And must gifts be returned after the engagement is broken?

If the marriage contract is concluded with all its pillars, then the spouses are permitted to enjoy each other. The Shar'i seclusion (al-khalwah al-shar'iyyah) takes the place of consummation in some rulings, such as the obligation of the 'iddah (waiting period) and the completion of the mahr (dower) according to the majority of scholars. Shar'i seclusion means that the spouses are alone together such that there is no real impediment (like illness), or legal impediment (like menstruation), or natural impediment (like the presence of another person) that prevents sexual intercourse. If a فسخ (annulment) or talaq (divorce) occurs after a Shar'i seclusion, then the 'iddah becomes obligatory and the mahr is completed according to some schools of thought. As for gifts, they are the property of the wife if they were part of the mahr, or stipulated, or customary; otherwise, they remain her property if the husband designated them as a gift.