RK - How far is the connection range from my smartphone to the RK robot?

The connection between the RK robot and a smartphone can work up to a distance of 20 m. This depends on the manufacturer and model of your smartphone, but also on other environmental influences.

Basically, your smartphone, not just the RK robot, must have BLE 5.
The software versions and BLE chip manufacturers used by your smartphone manufacturer in their devices also have an influence on the range.