Mazhar
Yes. Mazhar is a historically attested word in Arabic and Persian; it has been used as a laqab and in literary and Sufi contexts, and is attested as a given name in Persianate Muslim communities.
No. The root appears in Quranic Arabic in various verb and noun forms, but 'Mazhar' as a proper name is not a direct Quranic proper noun; its root (ظ-هـ-ر) is classical Arabic.
Yes. Because the term is used in Sufi literature to denote manifestation or the visible sign of the Divine, it carries established devotional resonance without being a title reserved for saints or prophets.
Mazhar appears mainly within Arabic- and Persian-speaking, as well as South Asian Persianate cultural circles; it is relatively rare compared with common Arabic names.
Traditional pairings include patronymics or compound forms such as Mazhar al-Din, Mazharuddin, or combining with family names; simple pairings like Mazhar Ali or Mazhar Hussain are also customary.