Many factors decide. Your result will depend on area treated, proper wound care, carefully suturing under the skin surface and on top with careful alignment. Amount of tension of closure and amount of movement will often impact the final result. Very important to minimize irritation and keep the site moist after surgery. Consult a physician that performs revisions for the specifics.
Less visible scar. The purpose of scar revision is to make a given scar become less noticeable. There are different means to accomplish this based on the location of the scar and why it is prominent. Techniques can be used to make a wider scar more narrow, reorient the scar in a more favorable direction, and/or camouflage it. Seek a surgeon with experience in this area.
Varies. This depends on the extent of the scar and success of the technique.
Usually favorable. Scars can be tricky. A scar would need to be carefully evaluated by a board certified plastic surgeon who should be able to tell you if he or she honestly feels the scar can be improved with scar revision surgery.