It's an extremely sharp opening and pretty trappy, probably prepared on a computer beforehand and unlikely he came up with miracle moves over the board,
Once a certain position has been gone into, as long as the other player is competent (>2000) and the time limit is long, even being Magnus Carlsen or Komodo may not be enough to help you.
Chess is not a game of luck. Kelires showed that he has better attacking skllls than top-class GM Fedorchuk
Can a 1700 beat a GM in a complex opening
It depends on who the 1700 is.
The guy above, Andreas Kelires, has swapped federation and plays currently for Greece (he lives in Heraklio, Creta since many years ago, where his father is a professor at the University), and has become a Grandmaster since two and a half years ago.
Kelires is now a 2508-rated GM.
The 600 point rating difference does not mean a 600 point difference in strength. If you want to know someone's current playing strength you need to look at their TPRs in recent tournaments, and not at the published rating. That game was five years ago. Fedorchuk was already in decline, but because the Elo system artificially slows down the rate of change of ratings he was overrated. Kelires was improving quickly and was massively under-rated.
This is just not a correct description of Fedorchuk's career. He's been rated above E2600 since January 2007, that's 12 straight years. He first peaked at 2671 in April 2008, dropped back down to 2603 in October that same year, then reached 2656 in April 2009, then dipped to 2619 in November 2009, reached 2674 in November 2010. Basically he's been bobbing up and down like that ever since. In short, Fedorchuk is a player whose results are very up and down all the time, and given that he was 2643 as recently as June 2018, he can hardly be considered a player in decline.
Kelires is now (August 2016) 17 years old and an IM with a rating of 2483. That gets him into the top 1000 active players in the world and rates him 25th in the world in the U-18 age group. In the past players with that kind of strength at that age go on to become very strong GMs.
Fedorchuk, by the way, still makes it into the top 200. What a world. A rating over 2600 barely makes the top 200 these days.
I won't pretend to properly understand the game that started the thread but the impressions it gave me are that Fedorchuk took his opponent too lightly and attacked crudely, assuming the 14-year old would crumble (but he didn't!) and Kelires was already much stronger than his 2175 rating.