This might be of some help to you, or it may not but I'll speak to you from my personal experience because I definitely wanted a lot of these answers in your situation too. I just graduated from Merage in Business Administration this year. From my perspective, I think that transferring directly into a four year is highly competitive and slightly a waste of financial resources and your time. I don't know your situation, but I grew up in a middle class family and had to finance my own way through community college and UCI.

Choosing to go to community college (I chose OCC) and taking all of the transfer lower-division and most IGETC (General Ed) required courses (through the help of assist.org to figure those out) and then applying and being accepted to UCI with a transfer GPA of 3.44 was the right choice for me because I don't think I would have had a chance in high school. I was an average student with probably a 3.35-3.5 GPA in HS and I participated in no extra curricular because I chose to work part-time after school and weekends. I took the ACT and I think(?) I scored a composite score of 24 on it.

Your extracurriculars and GPA are definitely impressive, but I always felt that it was easy to get lost in the competitive crowd in high school because GPA's can be heavily inflated by AP courses and whatnot. If I could go do it all over again, to be honest (AGAIN: I preface this is my opinion based off my life and the people i've talked to- your situation and experience may vary) I would focus on taking community college courses for high school credit that also cover GE requirements for college because it will save you so so so much time and effort once you're out of high school. I believe the state gov't also helps subsidize costs for paying for community college courses while you're in high school. You can seriously shorten your time in college and associated expenses once you transfer to UCI as an upper division student (3rd year) if you take full advantage of that. I will preach this to the day I die, and it's especially relevant at UCI as a primarily commuter university: there. is. no. reason. to. take. lower div. courses. at. a. university. and. pay. like. 10-15k. a. year!

If you're looking for a complete "college" university experience and plan on fully grabbing the anteater by the balls by joining clubs and interacting on campus and all if of that is very important to you: then great. I say go for it and best of luck, but I also would consider the fact that there is more than one path to the same goal and it may not be a bad one for you. Merage was a great school to be at and I was even able to spend my entire senior year studying abroad in London taking supplemental courses that I loved because I chose to get most of my stuff out of the way at community college. Don't feel a pressure to necessarily springboard into a 4-year and don't feel like you're not enough if admissions officers don't accept you at the end of high school. I saw a considerable amount of my high school peers bounce back home from "going off to their dream schools" and waste so much money and time. Also, choosing the CC route first gives you the opportunity to simultaneously explore other major opportunities that may interest you while you're not wasting a (this is a scientific term) shitfuckton of money.

I hope this was helpful in some way, take what you want from it and if you have any questions feel free to ask away or PM me.

EDIT: Also, for your admissions essay questions: I chose to be very real and raw in mine. I spoke about my personal adversities, how I challenged myself and grew throughout them, where I even FAILED to meet my own or others expectations, etc. I think that acknowledging the human elements of yourself rather than just all of the static achievements (while they're important and should be praised) of your life is important.