Arrival in CHina April 29, 90-day Double Entry Visa, what the latest date of departure?

You have to leave China before 27th July, it is 90 days stay duration counted from 29th April to 27th July. If you need to stay in China for more than 90 days, you can exit Mainland China, go to Hong Kong or Macau, then return to Mainland China for a new entry and another 90 days stay duration. You hold a double entry visa with 90 days stay duration per entry, you can make full use of your visa.