How can I remove a scar on my eyelid after a chalazion surgery?

Scars... Are permanent and cannot be removed. Generally the best scars on the body are on the eyelids because of the excellent blood supply and thinness of the skin. Scars take some time to mature, however, and don't assume their final appearance for 6-12 months. See a board certified plastic, facial plastic, or ophthalmic plastic surgeon for a definitive opinion.
You can't. While you can never eliminate a scar, you can reduce its appearance. Fortunately eyelid skin usually heals very well and the scars are difficult to see. It depends on how old the scar is. One of the best treatments for new scars is scar massage. 3 weeks after surgery, start to push on the scar pretty hard and make small circles with your finger. Do this 3 times a day for 10 minutes each time.
Depends on size. Depending on the size, treatment may consist of observation, steroid injection or excision/revision.
It can be done. The scar of chalazion is due to accumulation of fibrous tissue in the are of chalazion. You oculoplastic surgeon can inject small amount of firolitic medications that can disolve this tissue. Unless you mean deformity of eyelid due to surgery, in that case a surgical correction might be needed.