Question

Hcl reacts with a metal x to form a gas y which burns with a pop sound sodium hydroxide solution also react with same metal x to form gas y

Answer 1

Just because sodium hydroxide is reacting with the metal, this means that the metal is amphoteric. Metal X must be either of these Al , Zn, Pb, Sn, Be etc

Hydrogen is the gas which burns with a pop sound.
So,
Metal X = Aluminum
Gas Y= Hydrogen