and slides size to A4 or others (cm) in Keynote?
This is meaningless in Keynote as it is a pixel based processing application for video output, it does not translate to centimeters or inches accurately when printed to paper.
If your requirement is to print out an image at a set size on A4 paper, you will need to use Pages or any other application that can print to scale.
If you have no requirement to print to scale, Keynote can print slides, handouts, outline and notes with slides:
To set the paper handling from your printer; File > Page Setup > paper size; A4
To print: File > Print