1)? I'm not in the know, but I'm guessing that groups.io peeps are frantically trying to transfer groups whilst yahoo groups is messed up and isn't letting them do the transfers -- that's why I would guess groups.io isn't currently responding to support queries.
2)? a group we transferred last year, but the then-owner didn't want to move the current conversations yet -- so, there was a groups.io transfer, which effectively backed-up the group, then some months of further activity on the yahoo group, then we convinced the owner to let us move the activity -- so there was a couple months gap, on our groups.io home --
one of the mods went through the messages on the yahoo group, and copied/saved-as-pdfs, ones that were worth saving, then we put them in the Files of the groups.io group.