Which of the following compounds can show cis-trans isomerism?

Of the following configurations,the optical isomers are

Which of the following is a chiral complex? Here $en = \text{ethylenediamine}$.

Which one of the following has the lowest value of magnetic behavior?

$STATEMENT-1$: The geometrical isomers of the complex $[M(NH_3)_4Cl_2]$ are optically inactive.
$STATEMENT-2$: Both geometrical isomers of the complex $[M(NH_3)_4Cl_2]$ possess a plane of symmetry.

The $d-$ electron configurations of $Cr^{2+}, Mn^{2+}, Fe^{2+}$ and $Co^{2+}$ are $d^4, d^5, d^6$ and $d^7$ respectively. Which one of the following will exhibit the lowest paramagnetic behaviour? (Atomic no. $Cr = 24, Mn = 25, Fe = 26, Co = 27$).