(i) The oxidation number of hydrogen is +1 incase if it’s bonded with non-metals and have higher electronegativity than hydrogen. When hydrogen with metals or in some cases with atoms of similar electronegativity as compared hydrogen the oxidation number is -1 (eg. Aluminium hydride, Lithium hydride)

(ii) The algebraic sum of all the oxidation numbers in a neutral compound is zero, for a charged ion or molecular compound the sum is equal to the charge on the ion.

(iii) This option holds true for all cases.

(iv) Fluorine has the highest reduction potential of +2.87 in the entire electrochemical series, thus its tendency is always to undergo reduction and acts as the oxidizing agent. Thus it cannot give away any electrons, so it always accepts one electron to complete its outermost shell. Thus it always has a oxidation number of -1.