Who proposed the acid-base theory of ionization?

Which of the following is(are) true when $HCl(g)$ is passed through water?
$(i)$ It does not ionise in the solution as it is a covalent compound.
$(ii)$ It ionises in the solution.
$(iii)$ It gives both hydrogen and hydroxyl ion in the solution.
$(iv)$ It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule.

When soap is scrubbed on a stain of curry on a white cloth,why does it become reddish-brown,and why does it turn yellow again when the cloth is washed with plenty of water?

$R$. $K$. Patel,a chemistry teacher,explained the properties of inorganic acids in Std. $10$. He intentionally stated one of the properties incorrectly. Identify which one was wrong.

What is the $pH$ value for an acidic aqueous solution?

Which metal does not react with acid?