for a general equation Aa + bB cC + dD

Let Rate =k[A]^x[B]^y

Order of a reaction is the sum of the power of molar concentration of A and B reactant in the rate law equation (x and y) making a statement (iv) correct.

Order can be 0,1,2,3 or even fractional number depending upon x and y making a statement (i) correct.

x and y can be or cannot be equal to the stoichiometric coefficients of reactants of a balanced chemical reaction hence the order are determined experimentally making the statement (iii) false and statement (ii) true.