We can import the RAP from lower to same or higher versions of PRPC. I think it's not recommended to use the RAP from higher to lower versions as higher versions contain lot of new feature. If some thing goes wrong,We can't predict where exactly it went wrong.
down merge is a completely unsupported. The rule information has data about the rule which has a lot of data about the metadata of the rule. When you downmerge, the metadata properties might not exist in the rule heirarchy and the rule compliation and generation fails. Simple, backportin to lower version of prpc dont even think of it :)