The incorrect statement among the following is:

Let us examine each statement to identify the incorrect one.

$$Cr_2O_3$$ is indeed an amphoteric oxide. It reacts with both acids and bases. For example, it dissolves in acid to give $$Cr^{3+}$$ salts and fuses with alkali to give chromites. So statement (1) is correct.

$$VOSO_4$$ contains vanadium in the +4 oxidation state (as $$VO^{2+}$$). Since vanadium can exist in the +5 state, $$V^{4+}$$ can be oxidised to $$V^{5+}$$, making $$VOSO_4$$ a reducing agent. So statement (2) is correct.

$$RuO_4$$ contains ruthenium in the +8 oxidation state, which is a very high oxidation state. This makes $$RuO_4$$ a powerful oxidizing agent, similar to $$OsO_4$$. So statement (3) is correct.

The red colour of ruby is due to the presence of $$Cr^{3+}$$ ions replacing some $$Al^{3+}$$ ions in the alumina ($$Al_2O_3$$) crystal lattice, not due to $$Co^{3+}$$. So statement (4) is incorrect.

The correct answer is Option (4).