Transition metals exhibit variable valency.

The order of basic character of the transition metal monoxide is $$TiO > VO > CrO> FeO$$      because basic character of oxides decreases with increase in atomic number. Hence, oxides of transitional metals in low oxidation state, i.e. + 2 and + 3 are generally basic except $$C{r_2}{O_3}.$$

$${\text{At}}\,pH < 7,{\text{in acidic medium}}$$
$$MnO_4^ - + 8{H^ + } + 5{e^ - } \to $$     $$\mathop {M{n^{2 + }}}\limits_{{\text{(colourless)}}} + 4{H_2}O$$
$${\text{At}}\,pH = 7,{\text{in neutral medium}}$$
$${\text{MnO}}_4^ - + 2{H_2}O + 3{e^ - } \to $$     $$\mathop {Mn{O_2} + }\limits_{{\text{(brown precipitate)}}} 4O{H^ - }$$
$${\text{At}}\,pH > 7,{\text{in alkaline medium}}$$
$$MnO_4^ - + {e^ - } \to \mathop {MnO_4^{2 - }}\limits_{{\text{(green)}}} $$

$$2MnO_4^ - + {H_2}O + {I^ - } \to $$     $$2Mn{O_2} + 2O{H^ - } + IO_3^ - $$
$$MnO_4^ - + 5F{e^{2 + }} + 8{H^ + } \to $$      $$M{n^{2 + }} + 5F{e^{3 + }} + 4{H_2}O$$

No explanation is given for this question. Let's discuss the answer together.

$$\eqalign{ & Cr\left( {24} \right):3{d^5}4{s^1} \cr & C{r^{3 + }}:3{d^3} \cr & \mu = \sqrt {n\left( {n + 2} \right)} \cr & \,\,\,\,\, = \sqrt {3\left( {3 + 2} \right)} \cr & \,\,\,\,\, = \sqrt {15} \cr & \,\,\,\,\, = 3.87\,B.M. \cr} $$

Tendency of an element to form complexes does not depend on whether the element shows variable $$O.S.$$  or not.

Oxidation states shown by elements are as follows:
$$La$$  = + 3
$$Eu$$  and $$Gd$$  = +2 and +3
$$Am$$  = + 2 + 3 + 4 + 5 and + 6
$$Am$$  shows maximum number of different oxidation state due to its larger size and low ionisation energy.

$$2CuS{O_4} + 4KI \to C{u_2}{I_2} + 2{K_2}S{O_4} + {I_2}$$
( not given by $$KCl$$  ).
Fehling solution gives $$C{u_2}O$$  with reducing substances
\[CuS{{O}_{4}}\xrightarrow[\Delta ]{\text{strong}}CuO+S{{O}_{3}}\]

$$2AgN{O_3} + N{a_2}{S_2}{O_3} \to A{g_2}{S_2}{O_3} + 2NaN{O_3}$$