Arduino Bluetooth upload problem HC-05 v4.0

I upload code into arduino nano using a self-made PCB with bluetooth using this method. I was initially using Arduino Nano (chinese Clone, the one with CH340G) and Bluetooth module HC-05 (version 3.0) (Lets assume this bluetooth is BT1)

At command response for BT1

AT+NAME?
+NAME:H-C-2010-06-01
OK
AT+POLAR?
+POLAR:1:1
OK
AT+VERSION
VERSION:3.0-20170601
OK
AT+UART?
+UART:9600,0,0
OK

All the things were working perfectly till the new nano as well as latest version of bluetooth arrived.

Bluetooth problem: I was trying to configure the newer bluetooth BT2 and I faced the error highlighted in code.

AT Commands response for BT2

    AT+NAME?
    +NAME:HC-05
    OK
    AT+VERSION?
    +VERSION:4.0-20190815
    OK
    **AT+POLAR**
    **ERROR:[0]**
    AT+UART?
    +UART:9600,0,0
    OK

The problem I am facing is I am unable to change the state pin with AT+POLAR command. I think this version of bluetooth has different AT Commands. If anyone knows about this particular problem please help.

Also I tried uploading code using old bluetooth to a newer version of Arduino Nano (New bootloader OPTIBOOT) and it was successful. Needed to change the baud rate of program as well as Bluetooth to 115200.