If a board has four of a kind, let's say 9 9 9 9 J, how is the winner decided? Will kicker take part here?
Players will have cards in hand. Remember that TH has the rule of picking the best 5 possible cards. This means that users holding the best of Q K A in their hands will win. Otherwise, they will tie by picking the community cards.
9999J with two players holding 45 and 8T
They will tie because the best hand for them is 9999J in table.
9999J with two players holding 4K 5J
The player holding 4K will win because their final hands will be 9999K and 9999J (the other J does not matter).
However the players here:
9999J with cards 4K QK
9999J with cards 4K KK
will both tie with 9999K.
Yes, the answer is the kicker. If you have doubts, try always picking the best 5 cards for each player.