Are the KYC addresses listed in the blogpost (
https://blog.iota.org/claims-and-reclaims-finalization-e692844c505a) the old addresses of the old seeds or the new addresses of the new seeds where the foundation should send the tokens in this reclaim process?
This is important to know because afaik there's no way to know what your old addresses with the old seeds were anymore unless you for some reason had written them down somewhere.
The old (reused) addresses. Afaik you can check them with your old seed (history -> addresses), you might have to generate and attach a few because of the snapshot that happened in October.
No you can't, because the algorithm that generates the addresses has changed. So if you log in with the old seed, you won't be generating the same addresses you previously had.