After following the instructions shown below, if the reset works, you will have Windows 10 Technical Preview running! (and not back to 8.1!). There’s a confusion around about using the recovery tool and resetting from the menu.
This Friday, 27th March 2015, Gabe Aul has announced on their Windows blog that they are working on a new version of Windows 10 for their programme Windows Insiders.
Today Microsoft released Windows 10 build 10041 technical preview and promised releasing a new version of Windows 10 Technical Preview for phones very soon.