Glass reacts with $HF$ to produce

An element $(X)$ when burnt in oxygen forms a neutral oxide $(XO)$ and an acidic oxide $(XO_2)$. The element $(X)$ is:

$A$ cyclic skeleton of silicon and oxygen can be constructed by the silicate ion composition:

Which of the following is a mixed oxide?

Which of the following statements are correct?
$1.$ Charcoal can be obtained by heating wood in the absence of air.
$2.$ Charcoal is an impure form of graphite.
$3.$ Diamond is thermodynamically the most stable allotrope of carbon.
$4.$ Coke is used as an oxidising agent during the extraction of iron from its ores.

Which of the following is a good conductor of heat and electricity?