Can tooth contouring / reshaping fix cracked teeth?

Not Really. Tooth recontouring and/or reshaping is done only to enhance esthetics. For example, if one of your front teeth is too long, or has a rough endge, reshaping and polishing that will make it more attractive. Cracked and broken teeth can be fixed, but they will require different treatment. Your dentist can advise you about all your options, which are pretty amazing nowadays. All the best.
Not really. Contouring and reshaping usually eliminates minor faults and small chips in upper and lower front teeth and can give teeth a more youthful/more feminine or more masculine appearance. Cracks that run internally in teeth cannot be eliminated by contouring and usually need some form of restoration like a filling, onlay or crown to protect the crack from moving further into the tooth.
No. Tooth shaping will not repair a crack in a tooth. It may reduced the tooth so the cracked area no longer is traumatized. This can relieve symptoms associated with crack tooth syndrome. It can be maddening for both the dentist and the patient in deciding a treatment when pain from a cracked tooth is intermittent. Sometimes crowns are necessary as well as removing the nerve. Bacteria like cracks.
Depends. If the crack is minimal and horizontal rather than vertical, reshaping may delay the process. The assessment would be best made by your dentist.