There is no possible way, to my knowledge, to boot a Bondi G3 over USB(USB booting didn't come along until the AGP graphics based computers, and even there it's a miserable experience due to the speed of USB 1.1).
If you don't have an install disk, you can reset the password in Single User Mode. Boot into this by holding command+S-you should get a "verbose" boot(text output while booting) that finishes with a command prompt.
The general procedure-from the command prompt-is this although in my experience it does vary a bit with different versions of OS X
1. Mount the file system by typing "mount -uw /"
2. Type "cd users", which will navigate to the users folder. Then, type "ls"-the output is a listing of all user accounts on the system. Note what they are.
3. Navigate out of the user directory by typing "cd .."
4. Type "launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist"
5. Type "passwd username" where username is replaced by an actual name noted in step 2. You should be prompted to enter a new password for that account.
6. Reboot (you should be able to do so by typing "reboot"
