In Beijing can a 230V device be plugged into a 220v outlet

I used a 230V device in a 220V outlet. It worked well. Don't worry! But you need an adaptor.
As for the one with 120V to 100V outlet, one of my friends told me it also works. But you'd better further ensure that.

110 volt equipment wont usually work n 220 volt, or vise versa.

You will require a transformer to convert the voltage. Some mobile phone adapters and laptop power supplies as well as television sets and other electronic devices use a Switched Mode Power Supply (SMPS) inbuilt that converts the voltage as required.

Please check for voltage ratings on devices/ equipment you wish to use before you plug in.
This will save you some grief and lot of inconvenience.