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.