Possibility 2: 2 moves!
Some may have seen it
at once, others will have started to look for a way to attack Black's
last GIPF. But Gg3 can't be attacked yet, because any attempt would
leave Black a possibility to recycle pieces on the b1-i4 line and
remove the piece on f4 - disconnection Gg3 from the white piece
on e5. If White would have played 1.b5 or a2-f6, Black's reply would
have been 1…b1-d4;x - and out of problems…
So, White simply plays 1.c1-c3 (see diagram) and leaves Black no
way to form a row of 4. Yet, the correct answer is 2 moves!
In other words: this was a trick question! After White's move, Black
can still play (even though he has virtually lost the game yet).
He makes a move with his last piece, meaning that it is White's
turn again. White must make a move if you apply the rules very strict,
because only then Black is not able to continue the game.
However, here's a cheerful note: if you found 1.c1-c3, you have
every reason to believe that you solved the problem.