Sergash: Kaido Külaots is born in February of 1976 in Pärnu, Estonia, and so was 26 years old for the actual game. He became International Master in 1995, and Grandmaster in 2001, so the year just before the one when the actual game was played.
At the time I write this post, Külaots has been Estonia Champion eight times: 1999, 2001, 2002, 2003, 2008, 2009, 2010 and 2014.
At the time of the actual game and according to Chessbase, Külaots was rated 2531.
On the other hand, Magnus Carlsen was 11 years old, 5th grader and had no other title than chess Expert. He was rated 2127 in Chessbase for that tournament.
<2.d2-d4 e7-e6 3.c2-c4 d7-d5 4.Nb1-c3 d5xc4> In an earlier game played that same year, at the Norway Junior Championship, Carlsen had chosen 2.g2-g3 g7-g6 3.Bf1-g2 Bf8-g7 4.0-0 0-0 5.c2-c4 d7-d6 6.Nb1-c3 e7-e5 7.d2-d3 Nb8-c6 8.Ra1-b1 a7-a5 9.a2-a3 h7-h6 10.b2-b4 a5xb4 11.a3xb4 Bc8-e6 12.b4-b5 Nc6-e7 13.Nf3-d2 Qd8-c8 14.Rf1-e1 Be6-h3 15.Bg2-h1 ⩲ Carlsen vs D Kedyk, 2002, draw.
<5.e2-e4 Bf8-b4! => This is the 2nd most played move here. The #1 move, in appearances and that could be more precise, is 5.e2-e3 with the most played line going 5...a7-a6 6.a2-a4! c7-c5 7.Bf1xc4 Nb8-c6 8.0-0 Bf8-e7 9.Qd1-e2 = Tarrasch vs H Wolf, 1906, draw.
<6.Bc1-g5 c7-c5 7.Bf1xc4 c5xd4! 8.Nf3xd4 => This can also be played as a gambit: 6.Bf1xc4!? Nf6xe4 9.0-0! Ne4xc3 10.b2xc3 Bb4-d6! = with compensations Stelios Halkias (2579) vs. Arkadij Naiditsch (2665), Serbia Team Championship 2008 in Subotica, round 1, draw; note that 10...Bb4xc3?! 11.Ra1-b1 c7-c5 ▢ 12.Bc1-g5! (Andreas Skytte Hagen (2416) vs. Nikolaï Ninov (2507), BSF GM Copenhagen (Denmark) 2012, round 6, 0-1) Qd8-d7N! ⩲ Stockfish 11 - 64 bits POPCNT.
<8...Qd8-a5> The main line goes 8...Bb4xc3+! 9.b2xc3 Qd8-a5! 10.Bc4-b5+ Nb8-d7 11.Bg5xf6 Qa5xc3+! 12.Ke1-f1 g7xf6 = E Lobron vs Zsuzsa Polgar, 1990, 0-1.
<9.Bc4-b5+ Bc8-d7! => Main line : 9.Bg5-d2! ⩲ Gabriel Sanchez vs. Jose Garcia Padron (2420), Gran Canaria Open (Spain) 1989, 0-1.