Find RSSI of Mobile Device Without Connecting
You have two questions, but what makes you think you can't find these out?

When you want to know what a device can do (and thus can't do) you should check the devices' datasheet. I believe it is this file.

Bluetooth (and gsm) devices often work by sending AT commands. For example: "AT+PIO" to set/query GPIO pins of the module.
You can send "AT+RSSI?" to get a response on the RSSI value.



Not everything can be mentioned in the datasheet though. If you can't find any sources on it, it's most likely not a feature.

The only way to add a "validation function" within the bluetooth connection code, would be to re-write the firmware of the device.

But, you could:


Connect (with everyone using the right pin)
Check their RSSI
Disconnect if it doesn't match your criteria


I'm not sure if this module can have multiple connections, I didn't really see a way to disconnect a single connection. If not, you could even toggle the power to the module to "disconnect" the client(s).