Hello Parthiban,
I just checked in SE37 with the BAPI BAPI_QUOTATION_CREATEFROMDATA2 , i was successful in both creation and also deletion.
When you want to delete in addition to all the inputs update the field
UPDATEFLAG = 'D',
this field will be in the table QUOTATION_HEADER_INX of the BAPI, this helps in deleting the Quotation successfully,
Ty from your end also and confirm.
Although for creation i did not given value for the field. Check and let us know.
Regards,
Satish