fresh start with MDBT42Q , some specs before start toe code

Hello,
I have a simple project I want to run and want to know if I can use the MDBT42Q
I want to see I understand the configuration correct:

1. PI4 will be able to connect to him and send it 2 simple messages ("0" \ "1"), the it will change the digital output of 1 selected Digital pin(that will be connected to relay ) .
   so the PI is the client and the MDBT42Q will be the server , right ?
   
2. what is the approximately~ distance I can use for communication ?
   
3. can I connect an external antenna to the MDBT42Q and see if it's make any changes?
   
4. I have a working code on Arduino BLE( my problem with the Arduino is the distance , I get around ~ 4 meters only ), can I publish the code here and get some help converting it to java?
   
   

Thanks,