Hi,
as you said

"4. Why do you use root? It's not required."

in my case i have to use sudo gainroot.

And another thing, if record.py in MyDocs, even after sudo gainroot,it does not start camera and shows "permission denied"
thus i cannot save my videos in Mydocs folder

to use record.py in my phone. Record.py should be in root folder(home/user)