[Banana BPI-R4] how to enable I2C?

Hi! I use a latest snapshot but cannot find this file. I have a 3 questions:

  1. Whereis mt7988a-bananapi-bpi-r4.dts ?
  2. How to send information to OLED (ssd1306) ?
  3. There two pins for USB (con3 header on schematic) but if connect any devices nothing happen - not enabled ?