mod_ruby version compatibilities

Subject: mod_ruby version compatibilities

Hi,
I am integrating mod_ruby with Solaris Apache 2.2 package
Distribution.

I would like to know which versions are guaranteed to be compatible.

ie:
would mod_ruby.1.2.6 be completely compatible with mod_ruby.1.2.5 ?

how about mod_ruby.0.X.Y and 1.X.Y ?

To put it another way, If there is a non-compatible interface change,
which version number would get bumped up? in mod_ruby.A.B.C ?

(The reason for asking this is that the versions that are guaranteed to
be compatible can be added as an upgrade while the version changes that
may cause non-compatible changes may need to be treated differently.)

(By interface I mean any thing a developer may make use of in mod_ruby
while developing modules in mod_ruby. Includes configuration
directives and APIs)

Rahul.