Identify the inert gas used for filling balloons.

Which statements among the following are correct about Helium?
$(i)$ Liquid helium is used to sustain powerful superconducting magnets.
$(ii)$ Liquid helium is useful to carry low temperature experiments.
$(iii)$ It is a heavy gas.
$(iv)$ It is a flammable gas.

Which of the following statements is correct?

$XeF_{6}$ on partial hydrolysis gives a compound $X$,which has square pyramidal geometry. '$X$' is

$XeF_4$ reacting strongly with water gives .......

Which of the following reactions is an example of a redox reaction?