Elements of group $16$,except $Po$,are known as chalcogens because .........

The element which is the most abundant in the earth's crust is

When oxygen is passed through a solution of $Na_2SO_3$,we get:

Which of the following options is $incorrect$?

Given below are two statements:
Statement-$I$: $\alpha$ and $\beta$ forms of sulphur can change reversibly between themselves with slow heating or slow cooling.
Statement-$II$: At room temperature the stable crystalline form of sulphur is monoclinic sulphur.
In the light of the above statements,choose the correct answer from the options given below:

How many total statements are correct in the following?
$(i)$ $SO_2$ - antichlor,preservative
$(ii)$ $O_3$ - Disinfectant
$(iii)$ $Cl_2$ - Antiseptic
$(iv)$ $O_2$ - used in oxy-acetylene welding
$(v)$ $PH_3$ - used in smoke screens
$(vi)$ $HNO_3$ - Pickling of stainless steel