finddocumentsbyname() - if there are multiple documents with the same name, how

see
forum.appian.com/.../

Ideally, your process should update the existing document with a newer version instead of creating multiple documents of the same name. This will help you ease the querying process

If we do that, will previous versions still be accerssible in any way?

Yes. Appian maintains versioning on documents. If you want the user to be able to view the previous versions, you can write a simple expression to query the versions and generate the link to the versions. To the document URL, you would append

/suite/contents/GetContent.do?id={your document id}&version={the version you need}

you can get the max version (or the total no of versions) of the document using the document() function. Once you have this info, you can run an apply() function to generate the URL as stated above. Hope this helps.

So if I use versions, finddocumentsbyname() will only return the latest version of a single document. What if I don't use versions?

That's correct. The functions will always point to the latest version of the document. If you don't use version, then the function will return multiple documents. This can be a genuinely unique document having the same names or the same document uploaded twice. If you are looking for document revisions, I'd recommend uploading a new version of the document.