All of this is reasonably well known and has been played a bunch of times before. I never fully trusted these positions for Black though.
1. g1f3  1... d7d5 Duda was probably caught by surprise in the opening. It seemed so natural to expect 1.e4, which is Ian's main move. Also, Nepo has been playing the Petroff a lot with Black as of late, so he probably has some sense of where to put the most pressure. Duda's other option is the Najdorf, which Ian has crushed once already this tournament. I myself was also not expecting anything else on move 1, but the surprise clearly paid off. 2. g2g3  2... c8g4  3. f1g2  3... e7e6  4. e1g1  4... b8d7  5. h2h3  5... g4h5  6. d2d4  6... g8f6  7. c2c4  7... c7c6  8. c4d5 