Unable to reset Lumia 635

Hi,

Thank you for posting on Microsoft Community. I understand the inconvenience you are facing. I will certainly help you with this.

Since Windows 10 Technical Preview is still in development stage, certain features might not work in the appropriate way. We are looking forward to improve it and provide the best in the upcoming builds. 

As you want to reinstall Windows, I suggest you to get back to Windows 8.1 and try reinstalling Windows 10 Insider preview and check if it works. Kindly follow the below given steps:

Step 1: First you need to get back to Windows 8.1 and install latest update, and then try to get Windows 10 Insider Preview. Kindly follow the steps given in the below link to reinstall Windows 8.1 on your device:

http://www.microsoft.com/en-us/mobile/support/faq/?action=singleTopic&topic=FA142987

Step 2: After reinstalling Windows 8.1 with latest update installed try again to install Windows 10 Mobile Insider Preview by Windows Insider app. For assistance to install Windows 10 Insider Preview, refer the below given link:

http://windows.microsoft.com/en-us/windows/preview-download-phone

Hope this information helps. Kindly post back with the updated issue details for further assistance.

Thank you.