REST v10 API for Linked Records in Custom Modules

Please help me find linked records in custom modules via the v10 REST API. I did not make these custom modules, the previous Sugar admin did.

I am attempting to find linked records that are in custom modules we've added. I can't seem to do it. Most of the standard built-in modules work fine, for example - contacts, notes, leads, opportunities, etc.
We have five custom modules, and I know the prefix naming scheme and have been using in the query.

Example REST v10 API URL path:

https://{name}.sugarondemand.com/rest/v10/Accounts/{guid}/link/ra_{custommodulename}

In addition, I don't believe this is a module customization, but I've noticed we have a "Member Organization" sub-panel on the Account view which is shown as a account_account link in the Studio and I can't seem to query "accounts" that are linked to "accounts".

Further in addition, does one have to use a collection to get linked - emails, calls, meetings - for a record within a module? If so, how does one make the necessary changes to their OnDemand environment to allow for this?