Do i need to apply visa if i wish to travel to shenzhen from Hongkong?

If you visit SZ for no more than 15 days, the visa is not needed.

If your passport is Singapore, then you don't need visa to enter China.

If you have other passport, then you might be able to visit only Shenzhen without visa, not other cities!

(i know that European and many other passports can do it, but not sure for all other countries though)