Square planar complex of the type $MAXBL$ (where $A, B, X$ and $L$ are unidentate ligands) shows which of the following sets of isomers?

Identify the homoleptic complex(es) that is/are low spin.
$(A) \ [Fe(CN)_5NO]^{2-}$
$(B) \ [CoF_6]^{3-}$
$(C) \ [Fe(CN)_6]^{4-}$
$(D) \ [Co(NH_3)_6]^{3+}$
$(E) \ [Cr(H_2O)_6]^{2+}$
Choose the correct answer from the options given below:

$A$ complex of a certain metal has a magnetic moment of $4.91 \ BM$,whereas another complex of the same metal with the same oxidation state has zero magnetic moment. The metal ion could be:

Define coordination isomerism and hydrate isomerism.

Which complex among the following is most paramagnetic?

The metal ion whose electronic configuration is not affected by the nature of the ligand and which gives a violet colour in non-luminous flame under hot condition in borax bead test is