'Spirality'/ 'spiral symmetry' = pics on this page you will already
have seen
<http://users.indigo.net.au/don/ee/nonsense.html >  Or do you reckon
like John Vidale there that those lines mean nothing? (But the little
active bits at the ridges do...?)

Volcanic arcs?  You mean island arcs of the Western Pacific? Then I
see them like this:- <http://users.indigo.net.au/don/ee/bab.html>
...and like this:-
<http://users.indigo.net.au/don/ee/alaska.html>

Or continental margin magmatic arcs (e.g. South American Andes)?  Like
this:-
<http://users.indigo.net.au/don/ee/p2-page2.html>   (North and South
America in pre-scissored position (joined at the hip).  (Neither sort
of 'volcanic arc'  should be thought of in terms of plate tectonics.)

Hot spots?  I think so-called  'hot spots' (as they are termed these
days - different from the original entry in Seyfert's Encyclopedia of
Plate tectonics - in line with PT finagling things that don't fit -
shifting the goal posts) directly reflect the rupture of Pangaea and
resulting  hemispherical adjustment.  I'll post an illustration.

Palaeomagnetic dating of oceanic crust?  Not sure exactly what you
mean..  What about it?