Need some help with Access Control Lists

Please let me know if this isn't the right sub for this!

Hello everybody, I'm new to this sub but I have a quick question about a Packet Tracer school-work I have to do, and I'm kinda stuck and dont know how to proceede.

So the scenario is the following: There are 3 Networks (A,B and C). I should configure the routers in a way that with the help of ACLs network A and B can't see eachother but both of them can see network C. The routers are Connected in a Triangle so theres always 2 connections on 1 router. (I can't change cut the connections from the router / not route that connection)

The IP-Addresses I'm using for my networks are:

A: 200.10.20.0 / 26

B: 200.10.20.64 / 26

C: 200.10.20.128 / 26

And /30 masks for the Networks between the routers starting from 200.10.20.192 /30 (in total 3).

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How do I have to configure the routers now? I used RIPv2 for the routing but after some research I'm not sure if ACLs work with RIPv2. Do I have to use the static route?

Another question: I use standart access lists to deny a whole network to access another network but for some reason the whole traffic either gets permitted or denyed. How can I fix this and/or do I have to use inbound or outbound on the interface for the ACL.