1 It's hard. TOEFL is highly recognized in Korea. But I want to tell you that if the major you are applying for is not English teaching, you will not be allowed to enter this major if your language fails to reach Grade 4-5. (Half of them study languages for half a year before entering the major)
2. Renhe University is in Incheon, away from Seoul 1 hour, and its consumption is lower than that of Seoul, but it is 60,000-70,000 a year. To tell the truth, if you can't apply for a dormitory and get a scholarship, 70 thousand yuan a year will be very economical.
There are many opportunities to work in Korea, but they are all very tired. . . And the money given to China people is very small, but it is not bad compared with China. If you are not afraid of being tired, it is ok to use your holiday time to work hard.
Yes, either you already have a certificate or you can study the language again.
Think it over. I wouldn't come to Korea to study unless I had to. I hope I can help you.