At which stage of $PCR$,does the template join with the primer?

The different basic steps of genetic engineering are given below randomly:
$I.$ Identification of $DNA$ with desirable genes
$II.$ Gene transfer
$III.$ Maintenance of $DNA$ in host and gene cloning
$IV.$ Introduction of $DNA$ into host to form recombinant $DNA$
Which of the following represents the correct sequence of steps?

From the given combination of steps in $PCR$,identify the enzyme-dependent step.

On what basis are $DNA$ fragments separated in agarose gel electrophoresis?

Which of the following steps is $NOT$ a part of the basic process of creating a Genetically Modified Organism $(GMO)$?

Stirred-tank bioreactors have advantages over shake flasks because they