By theory your class 3 should at least 'pass' the probation
period of a year and within the 1 year you should not have any
demerited points.You should at least be 21 years old to apply for
class 4.
You know Jurong Stadium?If you go there you can see the office of
(Jurong driving school)and bring along your NRIC and Valid class 3
driving licence,And passport photos too. 
