what is the meaning of the pin out with 3.3V2, 3.3V3, 3.3V4 etc. I understand its 3.3 volts DC
It likely means that there are three 3.3 volt supply rails called: -

3.3V2
3.3V3

and

3.3V4

There may be a 3.3V1 and a 3.3V0 as well.
They may all be connected via 0 ohm resistors or possibly inductors or, maybe they are generated separately using several 3.3 volt voltage regulators. It's not uncommon to see this.