1.不对.
2.当一个小男孩和他爸爸走在乡下时,突然开始下起了大雨.
3.是的,由when或者while引导的句子都是时间状语从句.
4.从句是A small boy and his father were walking in the country,主句是it suddenly began to rain hard.
5.这句就是when放错了位置.如果用when,应该是A small boy and his father were walking in the country,when it suddenly began to rain hard.如果用while,应该是While a small boy and his father were walking in the country,it suddenly began to rain hard.