regarding invoice

Dear Vinay Garg...

You can maintain Single format Invoice is enough. If you sell your exempted/Zero rate goods you can enter at the Tax field as 0%.

BILL OF SUPPLY :

It's used for Composition Dealer....

COMPOSITION DEALER means Registered but., not on regular dealer / Normal Business under GST....

https://cleartax.in/s/composition-scheme-under-gst