Can i reset my iPhone passcode without erasing it?

You can only change the passcode if you know the current one. If not, you will need to erase the phone using one of the following procedures.

There is an Apple article that explains what to do if you have forgotten an iPhone or iPad passcode. Click on the following link: If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

If that option is not available, you will need to use a computer. See: If you forgot your iPhone passcode - Apple Support

Yes and no.

Yes, if you are able to access the settings on your phone. Set a passcode on iPhone - Apple Support

No, if you have forgotten the passcode and are now locked out of the phone. If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support