所有人都要提供吗？
-Yes.
在一个地方超过6个月，就要当地警察局提供证明？
-Just need one indicating that this person (specific name) has no criminal record during the entire period of his/her residence in China.
这个要公证吗？
-had better.
还是普通翻译过来就行了
-May be also fine (ask the Consulate to make sure).
