Hello I am travelling to China on 12th of April 2017 from Pondicherry, India.

I am quite concerned about my accessibility to be connected, as i would like to be connected to Internet, would I be able to use whatsapp and other social media apps, facebook, skype etc etc?

I will be traveling to Kunming, Hong Kong, Shanghai, Beijing, Xian, Lijiang. would I have to buy a new sim card for Hong Kong? Please advice.
Regards.