Can REST v5 Use v2 OAuth Keys?

I have an application that uses the v5 REST API. We're in the process of updating to v6 but the v5 integration is currently in use by customers as well.

Recently the v2 OAuth endpoint was released and I have a few questions:

- Can keys generated with the v2 OAuth endpoint be used with the v5 REST API?

- If not,  can the v1 OAuth endpoint still be used to generate keys?

Thank you.