Thank you very much @GregValiant!
I have learned a bit more about CURA software that is currently installed on my computer.
IT has one of the G-code flavors called "Ultimaker 2" in its machine setting, (Marlin, RepRap, Griffin are also options, but I suppose I should choose the type that matches my printer).
IT has a MONITOR tab to allow users to control the printer and send G-code.
So far, sending G0/G1 is all I have tried to do some basic linear movements, to move x, y, z to a particular position. The slowest step motor speed is 24 mm/min, or 0.4 mm/s (exactly same as you have tested ), which is O.K for me.
Now comes a question. CURA can save a G-code file, which I find useful. Is it possible to draw a shape and let CURA generate the G-code, then I can use the G-code to move the nozzle to the exact shape? Like the laser cutter, or CNC machine does. Is there a better software that can generate G-code from a shape?
Regards,
John