(i)
The lowest oxide of transition metal is basic because of some valence electron are not involved in bonding thus act as a base due to the availability of free electrons.

The highest oxide of transition metal electrons of metal is involved in the bonding. Therefore, these electrons are not available for donation. Hence, they are acidic in nature.

For example, $M{n}^{}\mathrm{O }$is basic, and Mn₂O₇ is acidic.

(ii)
Oxygen and fluorine act as strong oxidizing agents because of their high electronegativities and small sizes. Hence, they bring out the highest oxidation states from the transition metals.

For example, in OsF₆  and V₂O₅, the oxidation states of

Os and V are +6 and +5 respectively.

(iii)
Oxygen is a strong oxidizing agent due to its high electronegativity and small size. So, oxo-anions of metal have the highest oxidation state. For example, MnO₄^- , the oxidation state of Mn is +7.