@Aniruddha
On QGC, do the Parameters ever fully load? The reason I am asking is because if the connection to the GCS is not fast enough or strong enough for QGC to fully download the parameters then the other tabs like sensors and actuators in QGC will not appear. Which is why you are having an issue doing the level horizon from QGC. I know that QGC is seeing the video feed meaning you are connected, is the Green bar going across the full length of the fly view bar on QGC?