What are the positions of $N$ atoms present in the pyrimidine ring of nucleic acids?

In $DNA$,the consecutive deoxynucleotides are connected via

Identify the nitrogenous base of nucleic acid from the following that has a double-ring structure.

In $DNA$,the base units are linked by which of the following?

Hydrolysis of which of the following nucleic acids does not give an equal number of $A$ and $T$ or $G$ and $C$?
$(A)$ $m$-$RNA$
$(B)$ Single strand $DNA$
$(C)$ $r$-$RNA$
$(D)$ Double helix $DNA$

The presence or absence of a hydroxyl group on which carbon atom of the sugar differentiates $RNA$ and $DNA$?