X-COM: UFO Defense Cheats

Press [Ctrl] + C or [Ctrl] + G while in the battlescape screen to complete the current level with the results of the previous level.

It can be all too easy to save after a point where you can't advance any further, whether it's an unforseen rush of Aliens, or loss of funding via Country Infiltration. Not all is lost at that point. You will likely have to start over, but you can start over with all research progress and UFOpaedia information by copying certain files from one save to another.
First: Start a new game, and then save.
Second: Quit the game and copy the following files from your original save directory to the new save directory.
IE: You saved your original game in slot one and second save in slot 2, the directory would be /*whatever you named the X-Com directory.. drive:/mps/ufo/game_1/ for an example of the DOS version, then drive:/mps/ufo/game_2/ for the second save.
Files:
aknow.dat
research.dat
up.dat
soldier.dat (optional, if you've already got some good soldiers trained)
Third: load up the new game. You should have all the needed information.

It's really easy, once you have an avenger, make sure there are no passengers in the craft, be it human or mechanical bots and send it off to Cydonia. If you did everything right (which I really hope you did...for your sake), then a mission debrief/review (whatever you call it) will pop up and you get some amount of some resource. It was a long time ago and I couldn't remember if the loot was random or determined by your inventory, but there was a lot, including elerium. As you can see, the down side is that you have to wait till the end, which by then you would have plenty of everything:).

Select the item to be manufactured, but assign no engineers and leave the number to produce at zero. Then, assign as many engineers as desired but only manufacture one item. Use tanks with this trick to easily make money.