We have have Fed MP 1.0.1 running on 6.7. It can only collect from 6.7 child clusters. When trying to collect from a 6.6.1 cluster, we could not view alerts. We found there are too many differences in federation_config between 6.6.1 and 6.7 as well. Being on 6.7 or 7.0 across all instances is your best bet.
Thanks for the clarification but we haven't upgraded to 6.7 because we are using "Projects" a lot in order to predict our capacity.
Does anyone knows if "Projects" are back in 7.0 ???
They are not