Can I apply for 30 days - 2 entries Chinese VOA at Lo Wu? How much is the cost?

Sorry, the VOA just allows you to stay in Shenzhen for 5 days at most. You can't go anywhere out of Shenzhen. If you want a longer one, I suggest you apply a L type in advance.

Thanks Linda, please confirm your opinion .
I have just seen this comment :
BESIDES THE 5-DAYS SEZ VISA, YOU CAN ALSO GET A FULL CHINA ONE
(SINGLE AND DOUBLE ENTRY ONLY) AT LUO HU BORDER.
VOA means the one issued on arrival under some circumstances to be justified by applicant.
SEZ VOA means an "easy visa" to visit Special Economic Zone Visa 5 days and restricted only those economic zones.

I'd be grateful for your additional comments

Hii Luis, I think it is not correct information. Just like what Linda told you, you have to apply for a Chinese visa in advance through Chinese embassy/consulate. If you are now in Hong Kong, it is possible for you to get one there either.