Many thanks for the links NNNY for partial solution.
And you were right that I am bit scared to use xterm commands due to my total lack of knowledge about it.
However, i tried following:
I made a new QBW and selected 'hidden in SHOW button (to make it transparent).
I resized the Widget to 800 X 424 (max pixel size) and placed it to X value=0; So it covered the whole screen area.

Voila ! It gave me the protection of wrong handling and flexibility to scroll and answering incoming calls
Half work is been done. Rest half to remove that widget for enabling the
full (normal) usage of phone is bit tedious.
I had to long press and activate desktop editing mode and remove that widget manually and same process for putting that widget back on the screen.

Now; Is there a way to automate the process to remove or putting this widget back on screen by tapping few clicks or by other simpler way?

With kind regards and thanks,
Arvind