Dimethyl glyoxime forms a coloured complex with

The correct increasing order of stability of the complexes based on $\Delta_o$ value is $:$
$I. \ [Mn(CN)_6]^{3-}$
$II. \ [Co(CN)_6]^{4-}$
$III. \ [Fe(CN)_6]^{4-}$
$IV. \ [Fe(CN)_6]^{3-}$

The tendency to form complexes increases with ..........

Which of the following will not give a precipitate with $AgNO_3$?

Which of the following complexes is the most stable: $[Fe(H_2O)_6]^{3+}$,$[Fe(CN)_6]^{3-}$,$[Fe(C_2O_4)_3]^{3-}$,or $[FeCl_6]^{3-}$?

Aqueous copper sulphate solution (blue in colour) gives:
$(i)$ a green precipitate with aqueous potassium fluoride,and
$(ii)$ a bright green solution with aqueous potassium chloride
Explain these experimental results.