Is it correct that according to the Shaafi' Math-hab if the Dua is not recited in Janaazah Salaat or instead of four Takbeers only three are said, the

Answer

According to the Shaafi' Math-hab, four Takbeer and Dua are among the arkaan (fundamentals) of Janaazah Salaat. Omission of even one of the arkaan invalidates the Salaat. Therefore according to the Shaafi' Math-hab, the Janaazah Salaat will not be valid.According to the Hanafi Math-hab, four Takbeers are Fardh. The Salaat will not be valid if four Takbeers are not recited in Janaazah Salaat. However, Dua according to the Hanafi Math-hab is Sunnat. Hence if it was omitted, the Salaat will be valid although it is not permissible to unnecessarily omit it.