It's possible, but not through cheats in the game. At least there is no single experiment completion defined in the game code by default. However, you can open your save file with a SQLite database brower (
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, for example), find a table titled "tbl_challenge" and change the value for the experiment you want completed to 2. The list there is numbered (no names), so you will also have to figure out which number corresponds to which experiment. And here you won't be able to avoid relaunching the game a couple times to see, which challenge was modified. They are mostly in order, as far as I remember, so it won't take too much time. You can also set the ones you want to be uncompleted to 0 (not started). Then you save the changes and play the game.