What kind of chip is used in my circuit board?
It's some kind of an unknown dedicated toy Asian ASIC underneath that black epoxy blob. It is absolutely not reasonably repairable unless the problem is external to the blob. The construction is called Chip-On-Board (COB).
Look for lifted pads on that paper-based phenolic board or bad solder joints, especially on the flat cable. Try pushing or wiggling the leads, wires etc. and see if you can see any movement on the pads or protruding leads. Also clean the board with a toothbrush and 99% isopropanol - or failing that, at least hot water and detergent and let the board dry thoroughly- it appears to have gotten wet in the left lower corner.
If you can't find anything visible it's unlikely it's repairable, with the symptoms you describe.