You need to look up both the transfer admission and the graduation requirements of the four year schools you may want to transfer to.
For example, University of Oregon requires transfer applicants to have foreign language of high school year 3 (or 2 years taken in high school), college term 2, or high enough proficiency / placement test score for admission. For graduation with a BA degree, college quarter 6 or equivalent is required, but there is no foreign language requirement listed for graduation with a BS degree.
You may want to ask the department offering Mandarin courses about placement. If it offers a sequence for heritage speakers, that may be useful for you.