Generally No. The vast majority of visual development is complete by age 7 or 8. Some improvement in vision may be attained at ages up to 18 or so but the gains are modest. It's best to begin treatment as early as possible.
Nothing can. Amblyopia or "lazy eye" occurs when the brain decides to turn off the input of an eye that presents a different,weaker or out of alignment image. If caught early and the distortion corrected, vision can be retained.After many years,surgery might help with poor alignment, but the vision cannot be turned back on after the brain left it off for too long.
Unfortunately not. Lazy eye begins at birth (or before!) and must be treated aggressively before the age of 7 or so in order to have the greatest chance of it resolving. After the age of 7 the benefits of therapy drop precipitously as the brain becomes "used to" the eye being as it is. Neither natural or surgical/medical treatments are very effective by age 17. See a doctor to discuss your options.