U.S. citizens must obtain a visa to enter China unless you use the Visa-free transit (up to 240 hours/10 days) is available for travelers stopping in China for a third country. (https://en.nia.gov.cn/n147418/n147463/c183412/content.html) I would check the most updated information for whatever country you are coming from to determine your best fit!
Yes the FIrewall is OP. Make sure you download Alipay/Google translate (with Mandarin Loaded in) before arriving, As well as A map (Gaode) or Baidu Maps as most apps won't work without a VPN.
No...just wear what you would to any wedding.
you're cooked. better find someone who does. jk make sure you pre-downloaded mandarin for google translate though.
https://forms.gle/iM8sdDzfUaboYp3p7