Are age spots common? Is there any treatment for them?

Yes. What we refer to as "age spots" include seborrheic keratoses (brown stuck on bumps) and lentigoes (flat brown patches). Both are hereditary, very common, and we tend to develop more with time. They can be treated with liquid nitrogen (freezing), lasers, ipl, chemical peels, curretting, cautery, etc. Treatment choice largely depends on the number of spot and how thick they are.
Yes. Age spots become more common as people age. Some people use bleaching creams on them, although it is not very effective.
Yes. There are age spots that are intrinsic (seborrheic keratosis), and those that are due to chronic sun exposure (lentigo). This highlights the importance of sun protection. Treatment options include liquid nitrogen, chemical peels, photodynamic therapy, various light and lasers devices. Your doctor will choose the most appropriate treatment modality depending on the type of lesions.
Yes. "age spots" are more likely with lighter skin and with older age. Age spots can be treated with laser. Usually multiple treatments are needed. There are many types of skin changes that occur with age. Most are harmless but if you notice a "spot" that is irregularly shaped, has parts that are darker than other parts of the spot, is shiny, growing rapidly or is bleeding then see a doctor now.
Yes. The term "age spots" can mean several different things. One common meaning is a lesion called a seborrheic keratosis (sk). Sks are harmless thick dark plaques which often look like stuck on bark. They can be easily frozen off or shaved off surgically if undesirable cosmetically. Flat brown patches such as lentigos are more difficult and may need laser treatment to remove. All are very common.