Rohit,
blank pins on usb pins as replacements for PH00 and PH01 do not work, select, from schematic, pins that are N.C.
bananian 15.08 with BPi-M1+ hardware configuration uses UART4 instead of UART3.
I think this configuration is a copy-and-paste from BananaPRO which instead uses UART4.
To get a clear idea get the schematics of both and check differences on how A20 pins are used.
Regards
Snafutzz