reset to old firmware

Hi, I tried updating my printer in hopes of using the SN04 sensor that came with that box.

That didnt end well as the printer could not detect the Endstop when I try to home it after the firmware update.

My last resort is to go back to the original firmware. I went to the MarlinFW site and the old firmware does not have an easy way to upload the firmware into the board.

Any suggestions to get this printer back to the old firmware so I can use as opposed to having a large gift go to waste. This was given to me as a gift by a good friend and I would like to restore it and make sure the gift is not wasted. My thanks in advance.

Have you tries using youtube for help.

We read here you have a SN04 Proximity sensor, It would help if you stated what 3D Printer you have.
A few pictures of your 3D Printer could also be helpful if they show optional hardware.