How can I complete the prerequisites for Masters in Computer Science on my own?
I had two bachelors in Music and Art, minors in Marketing and CS. I then held a Computer Science career. When I went into the CS Masters program 7 years after obtaining my last bachelor degree, I had several deficiencies. I was accepted with two understandings. (1) I will complete the deficiency courses that are prerequisites to Masters courses I am to take, and (2) my current career in CS demonstrates I have the aptitude to succeed despite my entering the program with deficiencies.

I believe your best option is your #2, to enter the Masters program and complete the deficiencies in your coursework. When you write your letter of intent for application to the Masters program, I would describe these two aspects as they apply to your situation, personality, and drive to complete your degree.

Your other option for the US market is your #1, to complete the deficiencies from an accredited institution, then transfer the completed coursework with you when you apply. You must be careful with this option, to ensure the University you are to apply for a masters with will accept the coursework from the other institution. Before taking the coursework, it is best to call the University to ensure the courses will transfer.

This other option is best if you are under the following circumstances:


Currently working, and can take the deficiencies at night through an online University, or through a local college offering.
You will save money/time from taking the deficiencies from the alternate institute.


Your option #3 will not work, as they require the coursework credit from an accredited institution. Internationally, they usually require a demonstrated bachelors degree in CS. But post-bacc work needs to be completed as previously described.

Otherwise, you are best to just enroll in the University Master program and take the deficiencies there.

When I took the deficiencies for my masters program, I'd take deficiency courses one semester, and then the Masters courses that required the deficiency the next semester. In this way, except for the first semester, I was taking at least one Masters course every semester. Look at the University course catalog to see which courses have the least number of prerequisites that are your deficiencies, and then take those deficiencies first.