Hi Sudhakar,
Thank you for contacting Syncfusion support.
Query #1: Formula are not calculating if the cell index goes more than Z index.
Query #2: if cell having format thousand separator, commas it is not reflecting in export excel.
We confirmed that the above reported issues are defects and we have logged a defect reports for the same. The fix for these issues will be included in our Essential Studio 2019 Volume 1 release which is scheduled to be rolled out in the mid of March, 2019. We appreciate your patience until then.
Regards,
Silambarasan