Can there be an age limit for fibro myalgia, and could it cause swelling in hands and feet?

Probably not. Fibromyalgia ranges at least from adolescence and probably from early in childhood. Growing older does not spare anyone. Swelling (if objective) would have a different cause.
No age limit. The fibromyalgia syndrome [fms] is known to affect individuals from early childhood [nearly equal frequency in boys and girls] to the elderly. It can start at any age. In adults, fms is much [7-9 times] more common among females than among males. The most common age for fms is 40-60 years. The prevalence of fms increases with age up to about 70 years, after which it seems to decline.