Calls with longer duration not getting recorded / or getting recorded only for few seconds.
Battery saving app can cause a conflict and might terminate a process which is running for long (even longer than 30 sec) and that might cause longer running background process to be killed by these battery saving apps.
Audio/Video/Call records with longer duration not getting uploaded and can only be seen in “.settings” folder.
Battery saving app can terminate longer running processes and this might make only smaller files upload to server while the larger ones fail to upload. Disable or uninstall battery saving apps.
What is the Code to open the app when hidden?
Dial *666* (including stars) in your dial pad.
Is the app free or is there any hidden charge?
No the app is completely free. No hidden charge whatsoever.
Phone often displays a notification about spyware being detected
Try these steps to disable that alert: http://trackmyphones.com/b/disable-android-app-is-harmful-security-alert/
Can one track anyone else without any app installed?
No. You can do that only if “Android Device Manager” is installed on the phone by them and you have their Gmail id username and password.
Can one install spy/tracker app remotely to their mobile?
You can install remotely only if you know their Gmail id username and password. But if you install remotely you cannot make it work as you need to register the mobile by opening it and signing in.
My android mobile throws “Cannot open the apk file” error
You can try and download WinZip and open the apk in WinZip app, that should also do the trick.