HelloCustomer and thanks for your question.
Cats are prone to develop lumps and bumps on and under their skin and some are not harmful, while others may be dangerous, just as in humans. Your description is very good, and I will give you a list of possibilities of what this may be, but I'm sure you understand that a hands-on, in person examination of these areas are required by your vet, in order to obtain a specific diagnosis and then treatment, if necessary. The following information is from
"Papillomas and Warts in cats Papillomas and Warts: Grow out from the skin and look like warts or pieces of chewing gum stuck to the skin. Not painful.
Hematomas in cats Hematomas: Collections of blood beneath the skin, especially on the ears. Caused by trauma.
Tender Knots in cats Tender Knots (Abscesses): Frequently found after cat fights. Forms a firm swelling that becomes soft with time. Painful.
Cysts in cats Cysts: Smooth lumps beneath the skin. May grow slowly. Can discharge cheesy material and become infected. Otherwise, not painful.
Mycetoma Mycetoma: Mass or nodule beneath skin with an open tract to the surface draining a granular material. Caused by a fungus.
Sporotrichosis Sporotrichosis: Skin nodule with overlying hair loss and wet surface of pus at site of puncture wound or break in skin. Caused by a fungus.
Suggested Research: Infectious Diseases: Fungus Diseases.
cat grubs Grubs (Cuterebra): Inch-long fly larvae that form cystic-like lumps beneath the skin with hole in center to breathe. Often beneath chin or along abdomen.
Cat cancer When a Lump May Be a Cancer: Rapid enlargement; appears hard or fixed to surrounding tissue; any lump growing from bone; a lump that starts to bleed; a mole that begins to spread or ulcerate; unexplained open sore that does not heal, especially on feet or legs. Note: The only way to tell for sure is to remove and study the lump under a microscope."
Only your vet will be able to give you a definite diagnosis, once your cat is examined in person, so I hope you're able to accomplish this, ASAP. If these bumps are not bothering your cat, that's great, but try to have them checked out and hopefully, it will be something minor which is easily remedied.