In the event of a conflict involving Iran, the U.S., and Israel, China would maintain a stance of non-intervention on the military front, while offering support to Iran on the political and diplomatic fronts.
Most importantly, throughout the duration of such a conflict, China would not interrupt its trade relations with Iran. China would continue to purchase Iranian crude oil while simultaneously supplying Iran with substantial quantities of "civilian goods." During this entire period, the Chinese government would not disclose any details regarding China-Iran trade; however, on Chinese social media platforms, numerous private Chinese enterprises would likely be reporting on the situation.
Trump sought to use military force to compel Iran into submission, intending to leverage this outcome as a bargaining chip in negotiations with China. In Chinese parlance, this strategy is known as "杀鸡儆猴 killing the chicken to scare the monkey"—using a lesser target to intimidate a greater one. However, China would not allow him to succeed in this objective.
Simply put: China would not offer excessive support to Iran, but it would absolutely not permit the United States to completely topple the Iranian regime. If the U.S. were to escalate its military operations, China would respond by correspondingly escalating its trade in those aforementioned "civilian goods." As for what, exactly, those "civilian goods" might be—God only knows!
As for the Taiwan issue: I find it difficult to explain that to you in English.