How often are base level libraries/frameworks changing in incomparable ways?

In the JavaScript world, very frequently. If latest is 2.8 and I’m coding against 2.1, I don’t want answers using 1.6. This happened enough that I now always specify versions in my prompt.

That depends on the language and domain.

MCP itself isn’t even a year old.

The more popular a library is, the more times its updated every year, the more it will suffer this fate. You always have refine prompts with specific versions and specific ways of doing things, each will be different on your use case.