A while back, I ordered an IEIK Uno board. I received the wrong board, the seller didn't respond, I got a refund and got to keep the board. I have a legit Uno now, and I want to try messing around with I2C. When I try to upload something to the knockoff board, it get an error message that says:
avrdude: ser_open(): can't open device "\.\COM4": The system cannot find the file specified.
What makes you think its on COM 4 ?
Are you on Windows ?
If so unplug it from your computer and then open device manager
Expand the COM LPT section then[plug the board back in and see what it says.
If its shows up with any sort of warning triangle it may well be a driver issue.
If thats the case please take a picture near the USB connector and post it back here so we can see what you have.
Is there an option on the Tools -> Port menu? Clones and real boards don't use the same USB serial interface, so windows will assign them a different COM port number. If you don't go in and select the new port, the IDE will try to use the one you last had selected, which won't exist.
If tools -> port is greyed out or doesn't contain anything new when you plug in the board, you need to install drivers for the USB-serial interface on the board. Most clones use the CH340G (you can confirm by examining the markings on the IC near the USB port) - google for the driver and install it, and you should be good to go.