What is the magnetic moment value of $Cr(CO)_6$ in Bohr Magneton units?

Identify the pair of complexes that have the same magnetic moment (spin-only value).

The spin-only magnetic moment of $Ni^{2+}$ in an aqueous solution in Bohr magneton $(\mu_B)$ is .......

Which of the following complex compound$(s)$ is/are paramagnetic and low spin?
$(I) \, K_3[Fe(CN)_6] \quad (II) \, [Ni(CO)_4] \quad (III) \, [Cr(NH_3)_6]^{3+} \quad (IV) \, [Mn(CN)_6]^{4-}$
Choose the correct code:

Which of the following coordination compounds exhibit both optical and geometrical isomerism?
$a$. $[Co(en)_2Cl_2]Br$
$b$. $[Pt(NH_3)_2Cl_2Br_2]$
$c$. $[Co(en)_3]Cl_3$
$d$. $[Pt(NH_3)_4Cl_2]$
$e$. $[Pt(NH_3)_2Cl_2]$

The correct order of spin-only magnetic moments among the following is: (Atomic number: $Mn = 25, Co = 27, Ni = 28, Zn = 30$)