In Windows Phone (Nokia Lumia 525) I can't rename by Bluetooth name, and by default its showing 'Windows'. If all my friends (all are using Windows Phone) try to share some files through Bluetooth what will happen? Won't it will create an issue since all our Bluetooth name are same?
The Bluetooth name is the name of your device. There are some options to follow, depending on which Windows Phone model you have. But the best one is the easiest.
Connect your phone to the computer and change the name of your device using the Windows Explorer:
On your PC desktop, open Computer (or My Computer). Your device should appear under Portable Devices, and then right click on the device. Select Rename and enter the required phone name. Disconnect your phone from the PC. You can also use the Windows Phone app to change the name. To download and install the latest version of the app, go to www.windowsphone.com.
Its on Nokia site's FAQ