Malaysia passport holder to SZX

May I reconfirm that if holding Malaysia passport going to Shenzhen can VOA in Luohu right even though on Sunday? Is there any special requirement or condition of VOA such as inviting by China companies to China? Normally how long will it take to obatain visa, may be arrived in Luohu in the morning can I get instantly or need to wait until afternoon? Many thanks for your answers!