Agarose,extracted from sea weeds,is used in which of the following?

Which technique is used for the separation of $DNA$ fragments?

About gene gun method:
$I.$ This method is also known as biolistic technique.
$II.$ In this method,cells are bombarded with high-velocity micro-particles of gold or tungsten coated with $DNA$ in plants.
$III.$ Important crop plants like maize,rice,and wheat have now been transformed by this method.
Which of the statements given above are correct?

In addition to $Taq$ polymerase enzyme,which other thermostable $DNA$ polymerases have been isolated to be used in Polymerase Chain Reaction $(PCR)$?

What is the source of the $Ti$ (tumor-inducing) plasmid,which is modified and used as a cloning vector to deliver genes into plant cells?

What is true about $DNA$ polymerase used in $PCR$?