I downloaded a 2.5gb file using direct link , it failed at 1.75gb. The same file was present as a torrent so I renamed the broken file by replacing the original name with the torrent file name and force rechecked with tixati but it says "existing file with incorrect size" and it can't recheck it. when I followed the same procedure in Utorrent, Bitorrent and other clients it worked and downloaded the rest file completely without any errors . Due to this I've to keep two torrent downloaders in my pc .

My request to the developers is that please add this feature as soon as possible so that we don't have to rely on other softwares with malwares , ads etc. I noticed this fact 2 years earlier but waited hoping that the next update will resolve this issue but it hasn't been resolved till now. Kindly fix this please.

You cant. A torrent downloads in pieces of x size. When you download directly from a site its byte by byte. Its highly unlikely that your download had the same bytes downloaded as a torrent would possibly have at the same download percentage. You have to redownload it.