Which enzyme is known as molecular scissors?

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:

The diagram below represents a schematic of recombinant $DNA$ technology. Which enzymes are responsible for the processes $P$ and $Q$ respectively?
$\quad\quad P\quad\quad\quad Q$

The enzyme restriction endonuclease:

Which of these are most widely used in genetic engineering?

Give the types and functions of the Nuclease enzyme.