reset passcode without erasing data

Assuming you know the correct passcode, you wait the three hours, then enter the correct code. If you don't know the correct code, you have to erase the phone using a computer and your data will be gone. But if you have a recent backup, you can then restore your backup to the phone after erasing it.

If you don't know the correct passcode, this link details what you need to do to fully reset the phone --> If you forgot your iPhone passcode, use your Mac or PC to reset it - Apple Support

If you forgot the passcode, the only option is to erase and restore the phone. Any data on it that wasn’t already backed up or synced to the cloud is gone.

kusum96 wrote:

No, actually I forgot the passcode and phone get locked for 3 hours.I won't able to change/reset form another iPhone with same apple login. Above links, I tried. It doesn't work for me.

You cannot reset your iPhone from another iPhone. You MUST use a computer as the directions explain, with either iTunes (on a Windows computer) or Finder (on a Mac). If you don't have a computer yourself, you'll need to see if you can use a friends computer or visit an Apple Store to use one there.