If I have a multiple entry visa, can I enter before my originally submitted itinerary?

I would just like to know if it would be ok to enter before the original date as submitted in the itinerary during the visa application and if I can enter through a different place.

Specifically, I am applying mainly for a trip to Quanzhou, but if for example I am given a multiple entry visa, am I allowed to, say, make a day-long trip to Shenzhen before my planned trip to Quanzhou or would it raise red flags?