With IP, does Gradle reuse CC from projects that do not need to be reconfigured or does Gradle store 1 CC for all projects and reconfigure all projects, when eg 1 Gradle property is changed but only used in a few projects?

Afair IP also means CC per project

But what are the keys of the cache? And is there 1 build scoped cache or CC per project? Because currently, I have the feeling (!), everything is recalculated. Or can you reuse older caches, like with

configuration-cache.entries-per-key

In the second paragraph of the IP docs page:

This constraint unlocks two things: parallel project configuration and finer-grained caching of configuration results.

Incremental IP isn't ready yet. That's the next step, expected this year