RK Android Tool v2.3.9 does not natively support backup. However, you can use the companion RKDevTool (running simultaneously) to read partitions from a device in Loader mode.
Force-flash devices stuck in a bootloop by utilizing MaskROM low-level access. rk android tool v2.3.9
The Utility of RK Android Tool v2.3.9 in Firmware Management RK Android Tool v2.3.9 (also known as RK Android Tool v2