An enzyme catalyzing the removal of nucleotides from the ends of $DNA$ is

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: When a particular restriction enzyme cuts a strand of $DNA$,overhanging stretches or sticky ends are formed.
Reason $(R)$: Some restriction enzymes cut the strand of $DNA$ a little away from the centre of the palindromic site.
In the light of the above statements,choose the correct answer from the options given below:

Why is a vector necessary for obtaining the desired product in recombinant $DNA$ technology?

Give the types and functions of the Nuclease enzyme.

Give any two microbes that are useful in biotechnology.

Identify the incorrect statement regarding plasmids.