Is there a way that I can prevent new rows from being entered by the users?



If you give a user editor or admin access to your sheet, they will be able to add new rows. Viewers are not able to add rows, but they also cannot add data to the sheet. You could always send a full sheet update request which would let them edit the rows, but not add any new rows. Update request are good, but the update request URL is disabled after changes are saved.