Not 100% sure because the cloud part is not my area of expertise, but I an help with several general points.
Q1, integrating with SAP HANA: there's an ODBC driver available from SAP which can be used with any ODBC compliant tool (such as the Informatica platform, PowerCenter, and ICS / IICS). Performance might be troublesome sometimes, but that's a different story.
About SLP I can't tell.
Q2, products to connect to HANA: On behalf of SAP there's only one supported "gateway", as far as I know, and that's the ODBC driver mentioned earlier.
Injecting data into SAP R/3 systems is a completely different topic, here you have a good lot of choices from Informatica, mainly PowerExchange for SAP NetWeaver, available for both PowerCenter and the Informatica platform (not sure whether there's a PowerExchange for HANA available, I doubt it).
Q3, real-time integration: what exactly do you have in mind? Something like IDocs? API calls? Could you please be a bit more explicit what exactly you want to achieve here?
For SAP Hana you need to use the generic ODBC or JDBC connection. The version support for that depends on the ODBC or JDBC driver support.
Please refer the below articles regarding setting up connections for SAP HANA in IICS:
For integration with Ariba using IICS, you can refer the below Ariba connector guide
My requirement is to do a real time update of data from MDM to SAP HANA and Ariba and vice-versa.
No authoritative answer, but I dare to assume that in SAP HANA there is nothing like a built-in Change Data Capture (CDC) mechanism available. And the same probably is true for MDM.
What does that mean?
If you would have access to some CDC mechanism, then you could simply source these data and apply those changes in the "other" world (MDM = one world, HANA and Ariba = the other world).
But (again, if my understanding is correct) there is no such CDC mechanism available.
Using CDC mechanism on the underlying DBMS is not a viable approach. You can never be sure that the structures will stay the same after the next system upgrade, and you can never be sure that you get consistent CDC information that way. This is without any doubt a no-go approach. Period.
The only way which I see is that you look for "official" mechanisms to retrieve information from either world. After having "mirrored" the contents of either world in some central staging DBMS, you can then apply those "official" pieces of information to first update the staging DBMS and second the "other" world.
Very dangerous at best because you can NOT rely on information to be mirrored "just in time" between the staging DBMS and the "other" world.
In short: what you've been asked simply can't work without HUGE and in the long run useless efforts.
You will have to cut down this "generic" request to individual requests for which you can then look for some useful way to implement them. But a "generic" real-time replication between MDM and HANA + Ariba? I don't think this can be done in a useful, stable, and maintainable manner.
Again, these are just my 2 cents (without knowing anything in particular about HANA, MDM, and Ariba).