its better to raise ticket with My Oracle Support . They have clear idea on this. if anything goes wrong we can ask them only .
That is correct, FDM Classic last release is the 220.127.116.11.0 codeline. Beginning with the 18.104.22.168 version, FDM Classic will no longer be available, users will be required to move to FDM Enterprise Edition (FDMEE) in the 22.214.171.124 codeline.
FDM Classic is supported under lifetime support as you found, but that is only for the product as it stands. Any bugs or enhancements will not be resolved after the standard support cutoff, as noted in the Blog.