1. WEB - JS, CSS, HTML
2. IOS - Swift
3. Android?
4. Software testing
I do not have any experience in that. I just what to understamnd what is better, what about job oportunities and salary

Which, if any, have any interest for you ?

I am interested in mobile and web

Any platform in particular or available for all ?

Now I just want to understand what is better

Better is a relative term.
Some say Droid is better than Apple.
Some say Apple is just an over priced fruit..