So, purchased apple cider syrup is usually reduced much farther than the cider reduction I make for this, so I wouldn’t substitute it 1:1 for the 3 tablespoons without testing it first. I start with 480 grams of fresh apple cider and reduce it to 45 grams, so I’m retaining about 9% of the cider’s original weight. A purchased cider syrup is going to be even more concentrated, and the concentration will vary by brand. Since I haven’t tested the recipe with one, I can’t really give you a reliable substitution amount.

Thanks for checking. Yes, after the initial 5 minutes at 425°F, mine take another 10–12 minutes at 350°F. Oven temperatures vary quite a bit, which is why I also include the internal temperature in the instructions. The muffins should reach 195–200°F in the center before coming out of the oven, so if yours are still underbaked at 12 minutes, I would continue baking them at 350°F until they reach that temperature. I’d also be curious whether you baked a standard 12-muffin batch or made larger muffins, since that would affect the baking time.