It sounds like you are asking about drawing more than three cards in five card draw. In typical casino settings there is no limit on the number of cards you may ask for in draw. Home games may however have a limit of 2 or 3 as more people tend to draw and there is a limited number of cards.
Four of a kind.
In poker, it is very rare for a flush to beat a 4 of a kind. A 4 of a kind is a much stronger hand than a flush, so the flush would only win in very specific circumstances.
No, in poker, three of a kind beats a straight.
No, in poker, a three of a kind beats a flush.
No, in poker, a three of a kind beats a straight.
Yes, in poker, a straight beats a three of a kind.
Yes, in poker, a straight beats a three of a kind.
Yes, in poker, a three of a kind beats a straight.
Four of a kind beats a full house.
In poker, a 4 of a kind is when a player has four cards of the same rank, while a royal flush is the highest-ranking hand consisting of a 10, Jack, Queen, King, and Ace of the same suit.
Yes, four of a kind beats a straight. Only a straight flush (including a royal flush) beats four of a kind in a poker game with no wild cards, i.e. where five of a kind is not possible.
No, in poker, 3 of a kind beats 2 pairs.