public class Program
{
    public static void Main(string[] args)
    {
        List<KeyValuePair<int, string>> list = new List<KeyValuePair<int, string>>();

        list.Add(new KeyValuePair<int, string>(1, "A"));
        list.Add(new KeyValuePair<int, string>(3, "F"));
        list.Add(new KeyValuePair<int, string>(4, "G"));
        list.Add(new KeyValuePair<int, string>(2, "B"));
        list.Add(new KeyValuePair<int, string>(2, "C"));
        list.Add(new KeyValuePair<int, string>(3, "E"));
        list.Add(new KeyValuePair<int, string>(3, "D"));

        list=list.OrderBy(a=>a.Key).ToList();

        foreach(var item in list)
        {
            Console.WriteLine(item);
        }
    }
}

[1, A]
[2, B]
[2, C]
[3, F]
[3, E]
[3, D]
[4, G]

list=list.OrderBy(a => a.Key).ThenBy(a => a.Value).ToList();

list = list
        .GroupBy(kvp => kvp.Key)
        .OrderBy(kvp => kvp.Key)
        .SelectMany(g => g.Reverse())
        .ToList();

list
    .Zip(Enumerable.Range(0, list.Count), (item, insertOrder) => new { Item = item, InsertOrder = insertOrder })
    .OrderBy(x => x.Item.Key)
    .ThenBy(x => x.InsertOrder)
    .Select(x => x.Item)
    .ToList();