What is this StandardFirmata_ModifiedAll code doing?

Then no need anymore to modify it if I change my device to MEGA?

Maybe. Maybe not. It depends on exactly what you want the Arduino to be able to do.

So I only need to change the GUI code?

Maybe. Maybe not. It depends on exactly what you want the GUI to be able to do.

You can download so you might know the GUI appereance.

Yes, I could.

I also would like to add database that will record all the data for certain period of time.

So, do that.

This is really hard work.

Oh. Well, that will limit what you can accomplish.

I really hope the designer reply me soon,hmmm...

Still trying to get someone else to do the work, huh?