I saw a tutorial that said you could
ssh into a Pi Zero by using a different port and modifying various boot files, would this work on a Pi 3? Does the micro USB used for power have data lines?
While there are no data lines on the power port, there are other ways to gain access:
serial console session through GPIO (though a a console cable);
running a PPP daemon to connect via the GPIO serial port, and making a network connection with that;
serial console over Bluetooth; or
PPP over Bluetooth.
1 & 2 may be difficult on a Pi 3 due to the change in GPIO serial port specs. 3 & 4 may hit problems with availability of a Bluetooth serial profile for the Pi.
The micro-USB on a regular RPI have no data lines, it's power only. Besides that, what you read is a reference to the RPI
Zero USB hardware implementation is not like a 'regular' Rpi, Indeed all but the
Zero, present a 'usb hub' and not the
Zero master/slave USB port; the 'center' micro-usb is complete: data and power, while the other is power only.
On the software side, Linux Gadgets allows to offer serial, ethernet and other cool functionalities through the 'plain' micro-USB port.