Can we take multiple game branches(from one game), then combine the concepts into one?:
For a side project maybe, but for the jam, I personally would stick with one path and continue them branching even further (I'm not a stickler for rules but I'm also pretty sure that was implied by saying "picking A game made by another dev" instead of "picking ANY gameS made by other devS")
Someone else has already done it to good results though, so my gut feeling is exceptions may be made, but impossible to know for sure how the hosts will feel