It was very common and simple issue,,
1) Low iddling issue was due to,,,a relay was faulty under glove compartment and a wire was also changed under glove compartment,after that car's rpm went back to it's normal 1000 rpm.
2) cng missing was due to faulty coil (fixed over reducer unit),after changing that coil missing vanished immediately 
Total cost was 1800
Cng coil= 900
Relay and wire= 400
Labour= 500