I am creating a subclass for the Monk class. Kinda like an Arcane Trickster or Eldritch Knight, but with the Sorcerer spells list instead.
Although, I don't want it to be able to learn cantrips normally. Only spells fro levels 1 through 4.

How can I edit the subclass or Spellcasting feature to give the normal options, but like the Paladin or Ranger be prohibited from learning cantrips from that feature?
(the subclass will have a separate feature for learning cantrips from a limited list, so the solution can't be to have the subclass be totally unable to add cantrips in its sheet in other ways).

You cannot later the Spellcasting feature in any way.

Ok. But isn't there a roundabout solution to what I intend?
Instead of altering the spellcasting feature, maybe a way to prohibit the subclass from selecting cantrips? Or some other way...

Instead of adding the entire sorcerer spell list, you would have to add each individual sorcerer spell levels 1-4 individually under “additional specific spells.”