The pigment change you are seeing in your cats eyes appears to be pretty consistent with aging. Over the next few years, your cat may have even more of this mottled look to her eyes. From the pictures you provided, it seems that your cats pupils are the same size and can obviously constrict, and the darkening is not in large patches that have a lot of depth (which would be more consistent with melanoma). Obviously, without being able to examine your cat in person, I could not say for sure, but this does appear to be part of the cat aging process.
As for the bump on your cat's tail, it could be a bite, scratch, scar, or could even be an ingrown hair, most of which are of little or no consequence. However, cats can also develop cancerous tumors, cysts, and abscesses. Without seeing the bump in person and perhaps even conducting a needle biopsy, it is impossible to say what this bump is. I would recommend watching the bump and feeling it for changes in size, shape, or color.
However, when in doubt, bringing your cat for a veterinary exam is always a wise choice.