look at a Periodic Table
yes
Oxygen is an element - it contains no other constituent gases.
the noble gases
give names of gases
They consist of methane, and other gases, i think it also has hydrogen in it.
Gases naturally mix with each other when combined due to entropy.
Generally gases are miscible in each other; sometimes chemical reactions occur.
Unlikely other elements in the periodic table, noble gases rarely form compounds with other elements.
Fish let out natural gases. That gas is oxygen but they do not let out methane or any other gases.
No, inert gases should not be stored with oxidizing gases. Inert gases like nitrogen or argon are used to displace oxygen in storage containers to prevent combustion or oxidation reactions. Storing them with oxidizing gases could lead to potential fire or explosion hazards.
The active gas in the air is HYDROGEN
It is implied that you have already accounted for some gases and the question is about other gases. But you have provided no information about which gases you know about. Furthermore, there is no information on the context: is it the earth's atmosphere? That of another planet or satellite? Products of some chemical reaction?