I have a 3G WiFi Dongle from MTS in India and it supports an sd card i want to download files (torrent) direcly to the card.
When you connect the dongle to your PC, it should show up as a drive letter in My Computer (Windows) or appear on the desktop (Linux/Mac), if there is a formatted and working SD card in the slot. You need to change the settings in the Bittorrent program you are using on that PC to save files to the SD card.
When connecting to a Windows system for the first time there may be a delay of up to a minute or two as it figures out which drivers to install.
If you are asking if the dongle itself can download to your card without intervention from the PC, you can't do that. The firmware on the dongle would have to basically have a built-in Bittorrent peer and I can guarantee you no wireless carrier would do anything to actively encourage Bittorrent in that manner (they would prefer you not use it at all). It may be technically possible if you knew enough to change and customize the firmware on the dongle, but that's extremely difficult.
Also if possible to resume the downloads when reconnected to the network
Most torrent programs do this already. Just keep the program running and it should resume after your connection resumes. If your torrent program does not behave this way check out an alternate Bittorrent program.