Which one of the following complex ions possesses ionisation isomerism?

$\mu = \sqrt{15}$ is true for the pair :-

For the tetrahedral complex $[MnBr_4]^{2-}$, the spin-only magnetic moment value is $....$ (At. no. of $Mn = 25$) (in $BM$)

Given below are two statements:
Statement-$I$ : The number of paramagnetic species among $[CoF_6]^{3-}$, $[TiF_6]^{3-}$, $V_2O_5$ and $[Fe(CN)_6]^{3-}$ is $3$.
Statement-$II$ : $K_4[Fe(CN)_6] < K_3[Fe(CN)_6] < [Fe(H_2O)_6]SO_4 \cdot H_2O < [Fe(H_2O)_6]Cl_3$ is the correct order in terms of number of unpaired electron$(s)$ in the complexes.
In the light of the above statements, choose the correct answer from the options given below.

The spin-only magnetic moment in $BM$ of $[Fe(CO)_4(C_2O_4)]^+$ is:

$[Co(en)_3]^{3+}$ ion is expected to show