Unable to copy file, Access to the path is denied

here

if you are getting your json through a get

remember

return Json(result,JsonRequestBehavior.AllowGet);

JSON - A circular reference was detected while serializing an object of type 'System.Reflection

            var result = JsonConvert.SerializeObject(ds, Formatting.Indented,
                          new JsonSerializerSettings
                          {
                              ReferenceLoopHandling = ReferenceLoopHandling.Ignore
                          });
           
            return Json(result,JsonRequestBehavior.AllowGet);

fix HSTS issues

here

if you cant find save as template

just navigate here /_layouts/15/savetmpl.aspx

opening excel docs in SP in client

here

in order to have ellipsis in document library

u need

Name (linked to document with edit menu)