Does the EleksDraw firmware interpret the G02 / G03 circular interpolation. So far it has not moved after receiving any G-codes with G02 or G03
No. The Eleks firmware is Grbl 0.9i which had errors in the G2/G3 code, change to Grbl 1.1 and you will be able to use these commands.
Edit: I noticed after I posted that you are asking for the EleksDraw which is a CoreXY machine, getting Grbl 1.1 and CoreXY to play nice is possible but I haven't been able to get those and servo mode to work due to memory restrictions of the Nano. I think it's possible but without the boot loader and maybe dropping homing and some other features from the firmware when compiling.
But is not possible to replace the nano clone with a real arduino nano?
@robypez I'm not sure if this question is related to the original, but yes you can replace the Nano clone with another which of course includes the genuine Arduino.