Apart from a few new warnings for long-deprecated options it is compatible. HAProxy 2.0 is not a major version. Willy apparently just dislikes two-digit versions in the second place.
Exactly, I want directory listings to remain alphanumerically ordered, not like when you want to download Git and end up believing 2.9 is the latest one :-)
Yes, the same configuration should work between both. Although some options are no longer required to be set such as nbproc/nbthread. To be safe pass it through the configuration checker (-c on the command line).
