Open URL

Use  ISN_UIApplication.OpenURL method to open the specified resource. If the specified URL scheme is handled by another app, iOS launches that app and passes the URL to it. To determine whether an app is installed that is capable of handling the URL, call the ISN_UIApplication.CanOpenURL. method before calling this one. Be sure to read the description of that method for an important note about registering the schemes you want to employ.

Open App Settings Page.

The OpenSettingsURLString can be Used to create a URL that you can pass to the ISN_UIApplication.OpenURL method. When you open the URL built from this string, the system launches the Settings app and displays the app’s custom settings, if it has any. See the example below.

using SA.iOS.UIKit;
...

ISN_UIApplication.OpenURL(ISN_UIApplication.OpenSettingsURLString);

iOS System URLs 

You can also use iOS related system urls, there is plenty of predefined systems, URLs for opening different pages of iOS default apps. For example, you can find code snippet below to open system wifi settings compatible with all iOS versions. 

using SA.iOS.UIKit;
...

if(ISN_UIApplication.CanOpenURL("prefs:root=WIFI")) {
	ISN_UIApplication.OpenURL("prefs:root=WIFI");
} else {
	ISN_UIApplication.OpenURL("App-Prefs:root=WIFI");
}

Using URL Schemes

The OpenURL also used with URL Schemes API.