I had started a download on chrome, but after sometime wanted to stop it. There is no option available for that either in chrome app or in the mobile download manager. What should I do ?
You can go to download manager and long press on the entry and delete the file from options menu. Alternatively you can force airplane mode or switch off net/wi-fi to cancel the download.
In rare cases when its stuck in notification then go and force close the downloads app or clear data for download manager app.