Methane reacts with 1) water 2) chlorine 3) chlorine 4) nitric acid 5) hydrogen chloride 6) oxygen

Answer: 2, 3, 4, 6.
Explanation of the solution to the problem: methane is a limiting (saturated) hydrocarbon in which all bonds are single, which means that it is characterized only by radical substitution reactions.
1. Interaction with chlorine in the light (this is a prerequisite, otherwise the reaction will not work):
CH4 + Cl2 => CH3Cl + HCl;
2. Interaction with nitric acid (conditions: concentrated sulfuric acid, pressure and temperature):
CH4 + HNO3 => CH3NO2 + H2O;
3. Combustion (interaction with oxygen; complete oxidation):
CH4 + 2O2 => CO2 + 2H2O.