PR AND NATURALIZATION ON SINGH ROUTE

hi what's the process to get naturalize on singh route after 5 years residence in uk . as being married to British citizen naturalization is possible without PR ..

AND what the process for PR SAME AS LIKE BOTH WIFE AND husband are still married is any other requirements like British citizen employment history etc. or that's not a requirement . as other EU citizens have to prove that they are qualified person to be in uk as exercising treaty right . but to my understanding as returning British citizen EIND ruling apply so no need to show the financial sources of British citizen . any financial activities of residence card holder required or not.

and for naturalization again marriage certificate and living together proof in Europe and uk is required or not and same any financial requirement of either British citizen or the non eu spouse Is required or not .

in other words what's the criteria for PR UNDER SINGH ROUTE AFTER 5 YEARS RESIDENCE . AND FOR NATURALIZATION and is it better to apply for naturalization rather than permanent residence .

and if that's get refused can one still go ahead for PR as both of these are different categories. thanks in advance for your response.