Is it permissible for a young man to speak with a girl—even by phone—to ask for her hand in marriage before she gives him her home address and her guardian's approval, and does the ruling differ if he meets her in a public place with a mahram present?

If a woman is pleasing in her religiosity and character, and the young man intends to propose to her, there is no harm in speaking with her over the phone or meeting her in the presence of the suitor's mother or sister. The conversation should be limited to what is necessary to confirm a matter or inform her of something related to her, and then they should cease the conversation once the purpose is achieved, regardless of whether the engagement takes place or not.