Issue in GET route in asp.net mvc razor c# - asp.net-mvc-4

Question

I have 3 routes total in my code.
If I change the position of 1st with 2nd, then 2nd starts to work but 1st gives 404 error.
Am I doing anything wrong in below code?
This is GET route and works perfectly.
routes.MapRoute(
name: "Default",
url: "{controller}/{action}",
defaults: new {
controller = "Category",
action = "Index",
Category = UrlParameter.Optional
}
);
This is GET route and always give 404 error.
routes.MapRoute(
name: "Default1",
url: "{Category}",
defaults: new {
controller = "Product",
action = "Index",
Category = UrlParameter.Optional
}
);
This is POST route and works perfectly.
routes.MapRoute(
name: "Default_Without_Action",
url: "{controller}/{action}/{Category}",
defaults: new {
controller = "Product",
action = "GetProducts",
Category = UrlParameter.Optional
}
);

Answer 1

test if you put url: "{controller}" and see if this works
routes.MapRoute(
name: "Default1",
url: "{controller}",
defaults: new {
controller = "Product",
action = "Index",
Category = UrlParameter.Optional
}
);

Answer 2

I checked both routes and working fine.
RouteConfig.cs
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
//Route -1
routes.MapRoute(
name: "Default1",
url: "{Category}",
defaults: new { controller = "Product", action = "Index", Category = UrlParameter.Optional }
);
//Route - 2
routes.MapRoute(
name: "Default",
//url: "{controller}/{action}/{id}",
//defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
url: "{controller}/{action}/{Category}",
defaults: new { controller = "Category", action = "Index", Category = UrlParameter.Optional }
);
}
On initial/first request it matches the route-1 and calls the Index Action Method of Product Controller as shown in the picture below. Reason - We defined the defaults parameter for controller Products.
If we remove the defaults parameter from route 1 then on initial/first request route-2 URL pattern matches and Index Action method of Category Controller will be called, Reason - We defined the defaults parameter for controller Category.
Browser response with 404 error only when any request doesn't match with the registered URL pattern.