Thank you.
1. Try to add this snippet to the custom CSS
::selection {
background: #d60000;
color: #fff;
}
::-moz-selection {
background: #d60000;
color: #fff;
}
2. You can turn it off in Theme Options -> General -> Header Settings
3. Unfortunately, there is no such option in our theme.
4. Use this code
.back-top {
background:transparent!important;
}
Regards