Singapore Airlines upgrade, from business class to first

Hi There does anyone know if there are fare class restrictions when seeking an upgrade from business to first on singapore airlines as there is from Y to J?

No there shouldn't be pending award seat availability of course as F is next class up from J. Y is upgradable only on a full flexi fare and if there's no PE.

no i am asking if for instance you need to be full business rather than discount business 

There is only one J fare if paid with currency...you're paying a premium for the ticket, so it comes with all the perks i.e being upgradable. Have you tried looking on the SIA website? The fare conditions are explained there when you search for flights.