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