What happens if i reset my iphone ? Does it lock and become damaged ?

Here's how it works

When you turn on Find My [device] on your iPhone, iPad, iPod touch, or Apple Watch, your Apple ID is securely stored on Apple’s activation servers and linked to your device. From that point on, your Apple ID password or device passcode is required before anyone can turn off Find My, erase your device, or reactivate and use your device.

Activation Lock is enabled automatically when you set up Find My.

Before you give away your device or send it in for service

Make sure that you turn off Find My [device] on your device before you give it away or send it in for repair. Otherwise, your device is locked and anyone that you give the device to can't use it normally and Apple technicians can't perform service repairs. Just sign out of iCloud and then erase all content and settings. This completely erases your device, removes it from your Apple ID, and turns off Find My.

In iOS 10.3 or later:

1. Tap Settings > [your name].
2. Scroll down and tap Sign Out. 
3. Enter your Apple ID password and tap Turn Off.
4. Go back to Settings.
5. Tap General > Reset > Erase All Content and Settings.

In iOS 10.2 or earlier:

1. Tap Settings > iCloud.
2. Scroll down and tap Sign Out > Sign Out.
3. Tap Delete from My iPhone and enter your password.
4. Go back to Settings.
5. Tap General > Reset > Erase All Content and Settings.
6.  

Learn more about what to do before you sell or give away your device or before you send it in for service.