I own a group with 111 members and wonder if is possible to make a part only visible for a certain group rank? It means it will be invisible for the people who have lower rank.
Yes. But this is highly exploitable and shouldn't be relied on for major features. If you do intend for this, run checks on the server for the players position to keep them out of a room for example.
You need filtering enabled, creating a part in a local script will not replicated to the server, or other clients. Only the client it was created on.