Can we use (read & write) the characteristics request & response of XBee API BLE Service directly?

I am not fully sure of what it is you are asking. But yes, you can control all data going via the BLE interface via the API and Micro Python interfaces.

We can do that without srp(secure remote protocol) if yes how do that?

Yes you do need to use the SRP to enable as described at https://www.digi.com/resources/documentation/digidocs/90002273/Default.htm#reference/r_cmd__v__w__x__y.htm?Highlight=BLE

But you can use the Advertisements.