Is it dangerous to use a breast pump on a penis to milk it while a blood pressure cuff inflates on it?

If you are into doing things that can cause permanent tissue damage, to an organ most would like to keep healthy, you are welcome to try either. Be aware that you may not be able to recognize the tissue damage until it has occurred. If they end up needing to repair it, it is not likely to function as well as it did originally.

Any such gadget on the penis is dangerous and can do permanent damage. Please refrain from using any and all gadgets.

At your age, or any age, experimenting with unknown devices can result in serious results and or irreversible damage to your penis. Find a girlfriend or try masturbation, not infatuation.