Is uttering chaste words of endearment to one's fiancée, such as "I miss you," "I love you," "You are my soul," etc., Islamically forbidden during the engagement period? And is it permissible to look at the fiancée's pictures, including her charms, when feeling lustful?

A suitor is a stranger to his fiancée until the marriage contract is concluded. Thus, it is not permissible for him to be alone with her, or to be overly familiar in his dealings with her, or to flirt with her. His relationship with her is the same as with any other non-mahram. It is forbidden to look at her alluring features in pictures, and these pictures must be disposed of immediately. The suitor can avoid this شرعي (religiously unlawful) predicament by concluding the marriage contract with the fiancée and then postponing the wedding. What he does, in terms of flirting and looking at forbidden pictures, does not alleviate longing; rather, it intensifies it and arouses desire. Therefore, he must fear Allah and avoid temptations.