Okay, so for a open learning process:

Bypass/decoupling capacitors are for smoothing out electrical connections, so if an SCL line is continuously pumping out square signals , this is picked up by other parallel wires, which is bad.

So:
-Vin likes a capacitor to GND, to give the chip a nice stable power supply. Also, the LED's also like a capacitor to supply the LEDs.
-SDA, SCL and INT do not like capacitor, because the ripples in the voltages are the signal.

Next, tuning down V33 from the phone to 1.8V for the chip. This is because the SDA,SCL&INT run at 1.8V and the chip uses MIN-0.7*VCC. So, we use a linear regulator on V3.3 - with again capacitors on both sides.