It has everything that Arduino Leonardo has (electrically). Physically, it is just missing a power jack to save space.
Using the ATmega32U4 as its sole microcontroller allows it to be cheaper and simpler. Also, because the 32U4 is handling the USB directly, code libraries are available which allow the board to emulate a computer keyboard, mouse, and more using the USB-HID protocol!
The Dreamer Nano v4.0 is compatible with most Nano shield in the market. It's suitable for projects that require a compact size controller system.
Note: The pins supporting I2C/TWI is located at digital pins D2(SDA) and D3(SCL).
Dreamer Nano V4.0 1 unit.
Dreamer Nano 4.0 Wiki, Dreamer Nano 4.0 schematic, Dreamer Nano 4.0 Layout and Dimension, Arduino Leonardo versus Uno – What’s new, Arduino Leonardo product page, Arduino IDE, Atmega32u4 datasheet.