How to open Safari settings from a webpage on iOS 9.3+

Question

Here I find a solution on how to open Settings in iOS: How to redirect to ios settings in Safari using javascript in ios9

<input type="button" onclick="redirect()" value="Redirect">
<script>
    var redirect = function() {
        window.location.href = "prefs:root=Settings";
    }
</script>

But there are some problems with this solution on my iPhone 6s plus 9.3.2 (13F69): - this solution does not work on my iPhone, but works on iPhone 6s - the link to prefs:root=Safaridoes not work

So, I have 2 questions:

• How can I find out why this solution does not work on my particular phone?
• How can I open the Safari app in settings?