Fix bricked (I think) Uno R3

To make sure you didn't damage the board I would test if the USB-to-serial adapter works on the board. You can do this by sticking a ~1k ohm resistor between D0 and D1 (RX and TX) and then use the Serial Monitor in the Arduino IDE to see if what you type comes back. Don't forget to pull the resistor to make sure it's really coming back and not just echoing locally. If that works then something might be wrong with the Atmega328P. If it doesn't work then it could also be that the Arduino is driving the pins high or low, so test it when holding down reset too.

If you don't have a way to program the chip then the cheapest way to revive your board would be to just buy a pre-programmed Atmega328Ppre-programmed Atmega328P with the Arduino bootloader in it already. But that will only fix it if the board isn't damaged.

Since you already know how to use an Arduino as an ISP programmer I assume you only have one and can't reprogram the Atmega328P that way? It's strange that the bootloader would be damaged, but I don't know if Arduino write protect that part of flash, I'd assume it would do.

To make sure you didn't damage the board I would test if the USB-to-serial adapter works on the board. You can do this by sticking a ~1k ohm resistor between D0 and D1 (RX and TX) and then use the Serial Monitor in the Arduino IDE to see if what you type comes back. Don't forget to pull the resistor to make sure it's really coming back and not just echoing locally. If that works then something might be wrong with the Atmega328P. If it doesn't work then it could also be that the Arduino is driving the pins high or low, so test it when holding down reset too.

If you don't have a way to program the chip then the cheapest way to revive your board would be to just buy a pre-programmed Atmega328Ppre-programmed Atmega328P with the Arduino bootloader in it already. But that will only fix it if the board isn't damaged.

Since you already know how to use an Arduino as an ISP programmer I assume you only have one and can't reprogram the Atmega328P that way? It's strange that the bootloader would be damaged, but I don't know if Arduino write protect that part of flash, I'd assume it would do.

I have heard about Flip. Might that be the answer. If there is a way to flash a bootloader from an Uno to a Anet A8 V1.5 3d printer mb (this was to run a Marlin sketch for better hotbed safety), would it be wrong to think that I should be able to do the same with a Mega 2560 to an Uno?

gsd13 The ArduinoISP sketch seems to support the Mega board, since it's shown programming an Arduino UNO in the tutorial: https://www.arduino.cc/en/Tutorial/BuiltInExamples/ArduinoISP

Tried to loop test. Didn't work with any option you suggested above. I am missing a dll from  required dir that flip is calling for. I was reading that it is supposed to be in 3 different directories but I can't find one of them. I am going to keep working on it. Thanks for the help and any future advice.

D.