Combine the chicken, 2 tablespoons of the cornstarch, 1 tablespoon of the teriyaki sauce, 1 teaspoon of the garlic, and red pepper in a bowl; toss well.
Heat a large nonstick skillet over Medium-High heat. Add oil to the pan; swirl to coat. Add the chicken mixture to the pan; cook 6 minutes, browning on all sides. Stir in ½ cup of the broth, scraping the pan to loosen any browned bits. Transfer the chicken mixture to the inner pot of a 6-quart Instant Pot.
Combine the remaining 1 ½ cups of broth, peanut butter, remaining 1 tablespoon of cornstarch, remaining 1 tablespoon of teriyaki sauce, and remaining 1 teaspoon of garlic in a bowl; pour over the chicken mixture.
Close and lock the lid of the Instant Pot. Turn the steam release handle to the Venting position. Press Slow Cook, and use adjust to select More mode. Press [-] or [+] to choose 1 hour 30 minutes as the cook time.
When the time is up, open the lid and stir in the peas and carrots. Repeat the Slow Cook procedure, this time choosing 30 minutes as the cook time. When the time is up, the peas should be crisp-tender.
While the peas and carrots cook, cook the pasta according to package directions, omitting salt and fat; drain. Add the cooked spaghetti to the chicken mixture in the Instant Pot; toss well.
Sprinkle with scallions and peanuts; serve with lime wedges, if desired. Enjoy!