This is my opinion regarding your doubts.
In MAP, there is many activities or in the signalling call as application contexts(AC). Every AC has it’s own version for example Roaming No Enquiry using Version 2. So when the producer or vendors claim that MAP V3, you should ask them in which AC? then about the specification, yes it should have specification which they referred, for example for ETSI/GSM 09.02 has many version but which version they referred? then for release, it’s you mean the Software of producer?… some time release of software also mapped with signalling/MAP version to support some features like GPRS, CAP3 etc…