@j.rasch Hi - yes you can use our RDP Search API in order to confirm the correct RIC. If an instrument has been delisted the new delisted RIC will be indicated:
import refinitiv.dataplatform as rdp rdp.open_desktop_session('Your App Key Here') rdp.search('CLF.GQ')
Now if its not delisted - say VOD.L:
So the entry in row  will always give you the correct RIC - delisted rics have a ^ character in them. I hope this can help.
I'm not sure we can always rely on the logic described by @jason.ramchandani. RICs may be recycled. It doesn't happen very often, but it may happen. The infamous example is that the RIC "C" used to refer to Chrysler at one point and now it refers to Citigroup. ISINs are not reused. If you have an ISIN you can always get the current RIC. But all you have is a RIC and the RIC has been reused, then there's ambiguity and you need additional criteria to arrive to the result you're looking for. In the example of "C", if all you have is the RIC, it's impossible to say whether you're looking for Chrysler or for Citigroup without some assumptions or additional search criteria.