Sure. If you've got a reference you can check its type with the SvTYPE macro. For example (untested):

if (SvROK(sv) && SvTYPE(sv) == SVt_PVCV)
   warn("sv is a code reference (CV) alright.");
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As for your second question, you can check that an sv is a reference to an object of (or derived from) a given class using sv_derived_from() (untested all the way):

if (SvROK(sv) && sv_derived_from(sv, "Foo"))
   warn("sv isa Foo");
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And to check that a method is valid for a given class you can do something like (really untested):

if (gv_fetchmethod(gv_stashpv("Foo", 0), "Foo::bar"))
   warn("succeeded in finding Foo::bar");
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Now, I doubt I answered your all your questions, but you weren't exactly clear about what you're trying to do. Maybe you can explain in more detail?

-sam