Which of the following statement(s) is/are false?

The correct options are
A In $\left[PtC{l}_2\right(N{H}_3{)}_4{]}^{2+}$ complex ion, the cis-form is optically active, while trans-form is optically inactive.
C In $[Mabcd{]}^{n\pm }$ tetrahedral complexes, optical isomerism cannot be observed.
D In $[Mabcd{]}^{n\pm }$ square planar complexes, optical isomerism can be observed.
(A) In the complex $\left[PtC{l}_2\right(N{H}_3{)}_4{]}^{2+}$ both cis and trans forms are optically inactive due to presence of the elements of symmetry.
Thus option A is incorrect.
(B) Geometrical isomerism is not possible in $\left[Fe\right(C_2{O}_4{)}_3{]}^{3-}$. However optical isomerism is possible due to the absence of the elements of symmetry.
Thus option B is correct.
(C) In $[Mabcd{]}^{n\pm }$ complexes with tetrahedral geometry, no element of symmetry is present. Thus optical isomersim present.
Thus option C is incorrect.
(D) In $[Mabcd{]}^{n\pm }$ complexes with square planar geometry, plane of symmetry is present. Hence, optical isomerism is not possible.
Thus option D is incorrect.