The backup may not be encrypted with iTunes, otherwise is it not readable.
Depending on the iPhone or iPad version, the speed of the PC, the USB port speed and the timeliness of data backup, takes the process to be completing several minutes. Do not worry, the process will be terminate, even if it takes longer.
The reset process can not be stopped. If there is no backup in the iCloud or on the computer, all data will be lost irrevocably.