Last picture is most likely JTAG pogo contact points. For programming and testing. The board seems to be like 3-4+ layer board just based on the pictures. Also can't really tell you what chips those are with that quality of a picture. However the two little chips under the mounting hole on the picture in step 4 looks to be the DC Boost IC to keep constant voltage throughout the batteries life. The chip to the left of those boost converts is most likely the Bluetooth IC (just guessing by the location and the traces around it). Hope this helps :)