I do not think it is necessary. With all the resources on the internet, you can learn more online than you could in another country. Complete immersion can be very difficult and frustrating (especially as an adult).

No. Especially in this internet age. I honestly think my Spanish got worse in the three months I was in South America. Anything that you would do in a foreign country to learn the language, you can do online, and probably for free. Of course, that isn't to say that you shouldn't travel and see the world. That's a reward in itself.

Not about necessary, just because you like or not. Is a student going abroad illegal? Or if you have no money, I have nothing to say.

No. It depends on what your goals are. I used to think this was true and used to feel discouraged, because I'm not much of a traveler. But reading in another language is still quite fun and an enormous accomplishment! Plus with the Internet it's easy to speak with native speakers. :)

I don't think it's extremely necessary , but quite effective and quickly to get a good foreign language. Just like mandarin, because it's really hard to master.