How long is it supposed to it take a torn ankle tendon to heal?

Forever. I am not trying to be smart when i say forever. When you tear or rupture a tendon it is in the remodeling or repairing phase for your entire life. Once you get past the inflammatory phase which lasts about 3 days, then you go to the proliferative phase. This can last about 6-12 weeks. After that the remodeling phase which never ends. Much depends on age, general health and activity levels.
Ligament. Most ankle injuries are ligaments, however you can tear a tendon but it is not usually referred to as a torn ankle tendon. Depending on the severity of the tear sometimes they do not heal, if after 1 week there is no improvement of you can't put weight on your foot-see a doctor.
Depends. If it is small tear or complete rupture. For complete minimum 8 weeks.