The ability to regenerate limbs could sure come in handy (pardon the pun). Molecular and developmental biologists are very interested in how to “switch on” the ability to regenerate parts.

Selective breeding would only work in species that already have regeneration. For example, maybe some ghost shrimp regrow limbs faster than others, and we could breed the fast-regenerators together for several generations and might end up with a super-fast regenerator.

You seem to mean breeding together animals of different species, however. This doesn’t work. The definition of a species is that they can’t breed with other species and have fertile offspring. This definition gets a little fuzzy at the edges. For example, dogs and wolves do have fertile offspring. But you can’t breed a dog with a starfish.

What might work is to identify a gene that allows for regeneration and try to transplant it into the cells of the stump of an amputated limb. There are a lot of practical problems, including unknown risks and the likelihood that more than one gene is involved. But this is the most likely way to get the regeneration ability of one species into another.

Why do you think vertebrates like fish, amphibians, birds, reptiles, and mammals don’t have limb regeneration?

You might want to consider studying cell biology.

Yes it could be quickened by selective breeding, but animals that are utterly incapable of regeneration are not capable of breeding with animals that can. It would be like a human trying to have sex with a frog - it just wouldn't work!