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"Use Edit Log for transactions/masters, and digital signature for invoices/reports with Release 2.1. Download NOW!"
https://help.tallysolutions.com/docs/td9rel54/faq/6199.html

Is it possible to delete any Object viz., Master/Voucher through SQL query?

No. Only Select Statement in SQL Query is possible. Update or Delete queries is not supported.  In order to update or delete any object within Tally, one can use XML SOAP request.