Can a Decimator etc also fire ordnance in any direction or does this only apply to primary weapon? Thanks

There is no such thing as a 360 firing arc. There are ships which have primary weapons which can fire 360 degrees, but this doesn't change their firing arc. The primary firing arc is the shaded area printed on the base bounded by solid lines. Any auxiliary arcs are shaded and bounded by dotted lines.

Torpedos can only be fired out of the primary firing arc unless otherwise stated by the pilot card.

Decimator can only fire Torps forward.

As a quick addendum, when we see exceptions it's for things like the B-wing pilot Nera Dantels, or for (as it appears) the "special" rear-facing arc from the upcoming Ghost. But unless you see some specific exception called out, secondary weapons can only ever be fired using a ship's primary firing arc.

Same goes for missiles and cannons, btw.

No 360 degree arc.

Some ships that have attacks which can target ships outside of their firing arc. We often say these turrets have a 360 degree arc but that is highly misleading because of the terms used.

Some ships do have auxiliary firing arcs which can count as arc when called for but most secondary weapons are still restricted to the primary arc unless noted otherwise.