MDG Centralization

Hi,

I would like to know how can we consolidate MDG Data with scenario below:

We have Release 1, R2, R3 parallel landscape only R3 is S4 1909 rest are 1809 we refreshed from R3 to make one centralized MDG how can we merge R1 and R2 here in centralized system?

What data is coming here? is this client dependent? can we create multiple clients?

What is include in MDG data to become centralized?

Thanks

Mohammad