1. The flash chip is "BergMicro" 25Q32ASSIG. I'm not able to find any datasheet about the chip. The chip ID reads as "EF", which is the same as WinBond.
2. The chip runs on DIO mode. Pin 3 and 7 are connected to VCC. This makes GPIO9/10 usable. And user shall only program the chip in DIO mode.
Below is a photo of ESP-12E manufactured in May 2015 for comparison.