What is the magnetic moment of $[FeF_6]^{3-}$ (in $BM$)?

Which of the following coordination compounds would exhibit optical isomerism?

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 minimum paramagnetic behaviour?
(At. nos. $Cr = 24, Mn = 25, Fe = 26, Co = 27$)

The octahedral complex $[Co(NH_3)_5SO_4]Cl$ exists in two isomeric forms $X$ and $Y$. Isomer $X$ reacts with $AgNO_3$ to give a white precipitate,but does not react with $BaCl_2$. Isomer $Y$ gives a white precipitate with $BaCl_2$ but does not react with $AgNO_3$. Isomers $X$ and $Y$ are $.....$

Observe the following complex ions:

Complex Ion	Label
$[Mn(CN)_6]^{3-}$	$A$
$[Fe(CN)_6]^{3-}$	$B$
$[CoF_6]^{3-}$	$C$
$[Co(C_2O_4)_3]^{3-}$	$D$

Identify the option in which the unpaired electrons in the complex ions are in correct increasing order.

The spin-only magnetic moments of $[Mn(CN)_6]^{2-}$ and $[MnBr_4]^{2-}$ in Bohr magnetons,respectively are