China - customs do's and don'ts

I am entering China on a Z Visa (work visa).
I am planning on taking the following in:
1) Macbook Air (which I will purchase in Dubai and remove the outer packaging.It will be for personal use);
2) Huawei mobile phone for personal use (will include old apps such as Facebook, Instagram, music and pictures that I have saved on it); as well as an external hard-drive which may house the same information
3) A cross silver necklace (nothing too extravagant).
4) Clothes

Questions:
1) Will I need to remove any of the information on the mobile phone and hard-drive before entering customs?
2) Is it offensive to the Chinese government to have any Christian representation as jewellery or on devices?
3) Should I declare anything?
Oh and the mobile phone, hard-drive and Macbook Air as well as jewellery would be in my hand luggage