Can You Kiss Your Fiancé in Islam?
Question

I hope that you can explain the following to me: 

Does kissing the cheeks between an engaged couple mean that they must do the greater purification (Ghusl)? What is the case if that is on the mouth?  Does the latter invalidate Wudu in the case of a married couple?
Praise be to Allah.Can you kiss your fiancé in Islam?
A man and his fiancée are not married ; rather she is still a “stranger” (non-Mahram) to him until the marriage contract is completed. Based on this, it is not permissible for him to be alone with her, travel with her, touch her, or kiss her. 
No one should take this matter lightly, because the Prophet (peace and blessings of Allah be upon him) said: “If one of you were to be stabbed in the head with a needle of iron, that would be better for him than touching a woman who is not permissible for him.” (Narrated by At-Tabarani from the Hadith of Ma`qil ibn Yasar (may Allah be pleased with him); classed as authentic by Al-Albani in Sahih Al-Jami, 5045) 
Concerning the ruling on touching one’s fiancée or being alone with her, Az-Zayla`i (may Allah have mercy on him) said: “It is not permissible for him to touch her face or hands – even if there is no fear of desire – because she is still prohibited for him and there is no need for that.” (Radd Al-Muhtar `ala Ad-Durr Al-Mukhtar, 5/237). 
Ibn Qudamah (may Allah have mercy on him) said: 
“It is not permissible for a man to be alone with his fiancé because she is still forbidden, and Islam does not allow anything but looking, so she remains forbidden for him. And because if he is alone with her there is no guarantee that something forbidden will not happen. The Prophet (peace and blessings of Allah be upon him) said: “No man is alone with a woman but the devil is the third one present.” And he should not look at her with pleasure and desire, or in a dubious manner.” 
The Messenger (peace and blessings of Allah be upon him) warned us against being alone with a non-Mahram woman, and said: “No man is alone with a woman but the devil is the third one present.” (Narrated by Ahmad, At-Tirmidhi and Al-Hakim; classed as authentic by Al-Albani in Sahih Al-Jami`, 2546) 
Is Ghusl required after kissing a fiancé? 
With regard to the greater purification (Ghusl ) being required because of kissing, that is not the case. Rather the greater purification is required if semen is emitted or if intercourse takes place. 
Does touching a woman break one’s Wudu?
With regard to Wudu being broken by touching a woman, this has been discussed in question no. 2178 . 
And Allah knows best.