Did the project ever support Redhat 7.0? There are still people
using this version on low-end machines (p200, etc.).
Not as far as I know. If I remember correctly, the original plan was to
support 7.2 onward (with that collapsing to 7.3 and 9 due to limited
resources).
I would expect those low-end machines should be able to upgrade to Red Hat
7.3 without too many problems, at which point they could pick up further
updates from Fedora Legacy.