Which of the following statements is correct in the context of observing $DNA$ separated by agarose gel electrophoresis?

After staining,the $DNA$ fragments can be seen on the gel by exposing them to.......... light,which appear as.......... colored bands.

The blue and white selectable markers have been developed which differentiate recombinant colonies from non-recombinant colonies on the basis of their ability to produce colour in the presence of a chromogenic substrate.
Given below are two statements about this method :
Statement-$I$ : The blue coloured colonies have $\text{DNA}$ insert in the plasmid and they are identified as recombinant colonies.
Statement-$II$ : The colonies without blue colour have $\text{DNA}$ insert in the plasmid and are identified as recombinant colonies.
In the light of the above statements,choose the most appropriate answer from the options given below:

During the process of isolation of $DNA$,chilled ethanol is added to

The transfer of protein from electrophoretic gel to nitrocellulose membrane is known as

$PCR$ is used for: