Can a Wizard select an alternative capstone?

Question

More specifically, I'm building a Wizard and I'd like him to have the Perfect Body, Flawless Mind capstone (+8 Int).

I'm planning for him to be a diviner, specialized: Foresight, with the Pact Wizard (HH) archetype (that, as far I can tell, does not replace a wizard's capstone, since a wizard does not have one to begin with), and wonder if it'd still be legal to get the alternative capstone.

Does the natural 20 from Forewarned (Divination school) count as a capstone?

At 20th level, anytime you roll initiative, assume the roll resulted in a natural 20.

If so, am I able to select the alternative capstone in its place (since it's not an archetype)?

If not, could I do it as an universalist?

Relevant reference:

Alternative Capstone Ability

When a character reaches the 20th level of a class, she gains a powerful class feature or ability, sometimes referred to as a capstone. When a character reaches 20th level in this class, the following new ability can be selected instead of the standard 20th level class ability which would normally be gained. In some cases, a capstone specifies what ability it replaces. A character can’t select an alternative capstone if she has previously traded away her class capstone via an archetype. Clerics and wizards can receive a capstone at 20th level, despite not having one to begin with.

Answer 1

You can*

As a Wizard, you lose nothing to gain an Alternative Capstone. Specifically, from the rules you linked:

Clerics and wizards can receive a capstone at 20th level, despite not having one to begin with.

You can select one applicable Alternative Capstone. There is a better list on the Archives of Nethys Wizard page, which includes your desired one.

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*I have not played in a game with Alternative Capstones allowed. I would check with your GM that they're accessible and see if they want you to exchange a class feature despite the text; giving Wizards and Clerics more for free could significantly affect their game balance, especially at the highest level of play.