Does anyone know if i am still a cadet when I apply to an airline, does any airline offer jobs to FIs?
The term cadet only applies to unqualified people attending a course of training provided by an airline or perhaps if an apprentice. The choice of the term 'Cadet' is that of an individual company, there is no formal use. The OP is already a fully qualified pilot and when employed by an airline will need only to undertake a course for the aircraft type to be flown and any other specific in house courses.
I would say that a future employer cares little whether you are an instructor or not.