Is it recommended to do #upper digestive endoscopy before #ERCP (malignant obstructive jaundice)?

A 61-year-old man presented with obstructive jaundice was admitted to the endoscopy unit. Ultrasonography revealed dilated CBD with distal CBD stone. The patient underwent ERCP. The ERCP showed obstructed CBD and failure to pass the dye to the biliary tree. The scope also showed multiple duodenal sessile polyps. Also, complementary upper digestive endoscopy was done and confirmed the diagnosis of duodenal polyps. Multiple biopsies were taken for HPE. MRCP 2 days after the endoscopy revealed a pancreatic head mass and dilated both CBD and pancreatic ducts. Questions: 1- Is it difficult to differentiate between calcular and malignant obstructive jaundice by Ultrasonography? 2- Is it mandatory to do MRCP before ERCP? 3- Is it recommended to do upper digestive endoscopy before ERCP, especially in cases of malignant obstructive jaundice?