Hi I am a Malaysian currently in Hong Kong for work.

I am planning to visit Shenzhen and Zhuhai but on 2 separate dates. Must I apply for the double entry visa or will the single entry visa be enough?

Also, I have read that I can apply for the China visa at the China Visa Office in Wan Chai, Hong Kong. Must I go in person to apply or can I get someone else to do it on my behalf?