What are my chances of getting into UCLA under these circumstances?

I am a high school junior applying for colleges this fall.
-I have a 3.9 Unweighted GPA and a 4.0 weighted ( I know very low)
-1300 SAT (Will attempt a few more times (Highest SAT score for my grade))
-Low income community/Low opportunity school
-Treasurer of Humanitarians club
-Regular member of 3 clubs
-Link Crew Program
-Leadership
-Total of 8 AP classes by the end of senior year
-4 college classes in which I obtained A’s (One of which was Robotics)

I know these are low stats but are on par with previous years UCLA admits at my school. However my three questions are:
-1. What are my chances of getting into UCLA Computer Science Major?
-2. Can you have a backup major in case of rejection of preferred major? (I’ve heard it’s not possible)
-3. Is it possible to be accepted into a different Major and choose to double major with computer science?

Thank you so much in advance for taking the time to read this and answer.

  1. Average Stats for CS majors at UCLA 2019 was a 1540 SAT, 35 ACT and a 4.2+ capped weighted UC GPA.

Even if your stats were at the average, it is a Reach school regardless.

https://rogerhub.com/gpa-calculator-uc/

  1. UCLA does not consider alternate majors for the College of Engineering.

  2. If you want to double major, you would still have to be accepted into CS first and then major in your other area of interest but it cannot be into the College of Engineering.

2019 Freshman admit rates for UC GPA of 4.20 or above capped weighted and **not major specific: **
UCLA: 35%

2019 UC capped weighted GPA averages along with 25th-75th percentile range:
UCLA: 4.25 (4.18-4.32)

2019 Data:
25th - 75th percentiles for SAT totals:
UCLA: 1330-1550

Now that you have identified your Reach school, concentrate on some Match and Safety schools. Are you a CA resident?

Not likely given the current test scores and gpa. The school is test optional for 2020 but the gpa is still way too low.