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When talking about direction, “向” emphasizes the start or process, while “到” emphasizes the result of action:
向前进，向后转，“问君能有几多愁，恰似一江春水向东流”
到前面去，到后边去，到学校去，到生活中去
When talking about the direction itself, only “向” is applicable:
方向，指向，江河流向，性取向
When talking about arrival or till, only “到” is applicable:
到达，到站，到了，到学校了，皇上驾到
直到，爱你到永远，打破沙锅问到底，到明天，到那时，到时候
When talking about enough，only “到” is applicable:
功夫不到，火候不到
When talking about successfulness, only “到” is applicable:
找不到目标，找不到妈妈，买不到火车票，得到，“只有想不到，没有办不到”
When talking about completness, only “到” is applicable:
周到，面面俱到，照顾不到
At last, both "向" and "到" can be the lastname of a person.
