try below,
SORT IT_TAB BY VENDOR_NO, INV_NO, INV_AMT, INV_DT.
DELETE ADJACENT DUPLICATES FROM IT_TAB COMPARING VENDOR_NO, INV_NO, INV_AMT, INV_DT.
I'm not getting your last point, but you can try this.
try below,
SORT IT_TAB BY VENDOR_NO, INV_NO, INV_AMT, INV_DT.
DELETE ADJACENT DUPLICATES FROM IT_TAB COMPARING VENDOR_NO, INV_NO, INV_AMT, INV_DT.
I'm not getting your last point, but you can try this.