I'd say that 1 is not right with
for instead of
at as long as the idea is simply to say what time the appointment occurs.
a)
I'd like to make an appointment for 2 p.m., please.
b)
I'd like to make an appointment at 2 p.m., please.
c)
I have an appointment at 2 p.m.
d)
I have an appointment for 2p.m.
You could argue well that the latter example here is okay