Which type of isomerism is exhibited by $[Cr(C_2O_4)_3]^{3-}$?

The coordination compound with the molecular formula $[CO(NO_2)(SCN)(en)_2]Br$ exhibits which of the following types of isomerism?

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$a. [Fe(CN)_{6}]^{3-}$	$i. 5.92 \ BM$
$b. [Fe(H_{2}O)_{6}]^{3+}$	$ii. 0 \ BM$
$c. [Fe(CN)_{6}]^{4-}$	$iii. 4.90 \ BM$
$d. [Fe(H_{2}O)_{6}]^{2+}$	$iv. 1.73 \ BM$

Choose the correct answer from the options given below.

Which ion has the least value of theoretical magnetic moment?

The number of possible stereoisomers for the complex $[Co(en)_2Cl_2]Cl$ is $(en = \text{ethylenediamine})$.

On treatment of $[Ni(NH_3)_4]^{2+}$ with concentrated $HCl,$ two compounds $I$ and $II$ having the same formula,$Ni(NH_3)_2Cl_2$ are obtained. $I$ can be converted into $II$ by boiling with dilute $HCl.$ $A$ solution of $I$ reacts with oxalic acid to form $[Ni(NH_3)_2(C_2O_4)]$ whereas $II$ does not react. Point out the correct statement of the following: