Problem $2.$ Linked Lists. $(35\%)$

In a singly linked list L with more than three nodes, a pointer p points to a node that is guaranteed to be neither the first nor the last node. What are the purposes of the following code blocks $(15\%)?$

a$.$

$q=L$next$$next;

$q$data$=q$next$$data;

$q$next$=q$next$$next;

b$.$

$q=L$;

$t=p$ data;

$p$ data $=q$ data;

$q$ data $=t$;

c$.$