Citizenship questions

I’m an abc who has lived in the USA my whole life, both of my parents are Taiwanese citizens. I have both an American Passport and Taiwanese passport. I’m looking to stay in Taiwan longer than the 90 days permitted. So I read that I’m applicable for citizenship(Id card) since both of my parents are citizens and that I’m under the age of 20 still. What I’m wondering is that if I do apply for citizenship(ID Card) while I’m there can i stay pass the 90 days i was originally allow since I am a citizen now? Also would I automatically be required to do military service, or do I have the 180 days thing.
any feedback would be much appreciated :slight_smile: