SF_10.1, SF_10.2, SF_11.0, SF_11.1, SF_11.2, SF_12.0, SF_12.1, SF_12.2, SF_13.0, SF_13.1, SF_13.2, SF_13.3 - https://docs.sitefinity.com/for-developers-query-pages

QueryPages_GetPageNode_NativeAPI.cs

using System;
using System.Linq;
using Telerik.Sitefinity.Modules.Pages;
using Telerik.Sitefinity.Pages.Model;

namespace SitefinityWebApp
{
    public class QueryPages_GetPageNode_NativeAPI
    {
        public PageNode FindPageNodeByIdNativeAPI(Guid pageNodeId)
        {
            PageManager pageManager = PageManager.GetManager();
            PageNode node = pageManager.GetPageNodes().Where(n => n.Id == pageNodeId).FirstOrDefault();
            return node;
        }

    }
}