how to display this create instacnce and delete instance button
at device page
InternetGatewayDevice.WANDevice.1.WANConnectionDevice.1.WANPPPConnection
InternetGatewayDevice.WANDevice.1.WANConnectionDevice.1.WANPPPConnection.1
Sounds like the user does not have the appropriate permissions. Or the CPE is sending <Writable>0</Writable> for the InternetGatewayDevice.WANDevice.1.WANConnectionDevice.1.WANPPPConnection parameter.
To determine if this is the case, got to Admin → Config and create a new config entry with a key of cwmp.debug and value of DeviceID.ID = "acs_id_of_device". Finally, refresh InternetGatewayDevice.WANDevice.1.WANConnectionDevice.1.WANPPPConnection and look at the ParameterInfoStruct, it should look similar to this:
