Numbers import one of the earlier (non-protected) versions?
Nope. An attempt to open the January 31 copy from the Time Machine drive got:
Import ErrorThe document is encrypted and can’t be opened.
Good thing I finally figured out what the password was.
ryck
UPDATE: I did another test with Numbers. Since it was not able to open the file stored in my Time Machine backup, I thought I'd try it on the original file, with the password now removed.
Numbers opened the file without incident, other than a few cautions about not retaining some formatting. The file is many pages with several links and everything worked fine.