Catalyst is a substance which is required in very less amount to catalyse any reaction. So (iii) is wrong.

Chemisorption involves the formation of chemical bond through which an adsorbate gets adsorbed on adsorbent. So if the interaction between the reactant molecules is large enough, formation of activated complex becomes easier using a catalyst. So (iv) is wrong.

When the same reactants may give different product by using different catalysts this is known the selectivity of a catalyst.

For example, during the catalytic hydrogenation of alkyne, if we use Palladium as a catalyst, the product will be alkane. But if hydrogenation is carried out using Lindlar catalyst, we get alkene as a product.

So option (i) is correct.

Using a catalyst, it does not interfere with the amount of heat absorbed or released for a chemical reaction. So the change in enthalpy is independent of catalyst. Therefore, (ii) is also correct.