2+2 means studying in China in the first and second grades and studying in Germany in the third and fourth grades. Tuition fees generally do not need to be paid extra, because in the past, it was generally in the form of inter-school exchanges, but living expenses must be taken care of by themselves.
As for the third question, I personally think Spanish is the best job prospect now.
Speak German first. German is spoken in five countries, such as Germany, Austria and Switzerland. The total population is about 1 billion. More than 70 universities in China enroll German, including 20 German master's programs and 3 doctoral programs. Take a school with 50 students as an example. You can count how many German graduates there are every year, and many German students go abroad to study. Such figures are under great pressure in China.
In French, the teacher is ok and has a master's degree. Employment is similar to German. Although the population is better than German, there are many jobs in China. The most important thing is that many people will be sent to work in Africa and South America after graduation, which is even more difficult.
The employment situation of Arabic is better, but there is no master's degree in northern languages. I want to remind you that Arab countries discriminate against women because of their religious beliefs, and China women have a poor reputation in Arab countries. It will be very troublesome for girls to learn Arabic and get a job. If you are a girl, you must be careful.
Finally, if Spanish is spoken less in China, it can be regarded as a small language in the true sense, and the employment is quite good. As far as these four languages are concerned, the employment situation is the best. However, in this extremely small language, the number of teachers is generally limited, because there are few professors, so it cannot be measured by the number of professors.
As for the exchange abroad, just look at the exchange programs between North Language and schools in these countries. But in fact, if you really want to go, you can also take a language test and apply for going abroad yourself.