1. Here is the long answer:
The civil service departments such as the government offices, embassies and schools are closed on the legal holidays. Elementary public service establishments like the public transport system run normally to facilitate the locals and visitors on their basic living and travel; however, please note that the banks and post offices only have their major branches opened on China public holidays, so it is better to go to those branches in the preposterous business districts in big cities, or arrange your money and post matters in advance. Most of the hospitals run during holidays, but maybe only the basic departments are available, without some famous specialists.

Hope this help.

Chinese Customs also work? There shouldn't be a delay for packets to other countries?