Which spell can turn me into a unique type of creature or specific example

Just in case I misinterpret any of the wording, would shapechange or true polymorph allow me to turn into a specific/unique creature?

True polymorph:
"Creature into Creature. If you turn a creature into another kind of creature, the new form can be any kind you choose that has a Challenge Rating equal to or less than the target’s Challenge Rating or level. The target's game statistics are replaced by the stat block of the new form, but it retains its Hit Points, Hit Point Dice, alignment, and personality.

The target gains a number of Temporary Hit Points equal to the Hit Points of the new form. These Temporary Hit Points vanish if any remain when the spell ends.

The target is limited in the actions it can perform by the anatomy of its new form, and it can't speak or cast spells."

Shapechange:
"You shape-shift into another creature for the duration or until you take a Magic action to shape-shift into a different eligible form. The new form must be of a creature that has a Challenge Rating no higher than your level or Challenge Rating. You must have seen the sort of creature before, and it can't be a Construct or an Undead."

I didn't include the rest of their descriptions as those weren't really relevant to my question.

I'm mostly asking this cause I wanted to turn into one of the princes of elemental evil for a semi-oneshot game, and just wasn't sure if I could turn into one since they were a unique creature and not really a type of creature.