No. In Poker all hand combinations are formed from 5 cards, even pairs(other 3 cards that form the hand are kickers). So if you only have 4 cards of the same suit and no other legitimate hand, the 3 of a kind would win.
However, poker is a game with many variations and different "special" rules and I remember reading about a game that actually allowed 4 card flushes(I think it was ranked just above 3 of a kind), but this is very very very unorthodox and you won't find it in online card rooms and I would be surprised to find it in any casino.
In poker, a flush would typically beat a 3 of a kind.
No it does not
No
No, in poker, a straight does not beat three of a kind. Three of a kind is a higher ranking hand than a straight.
No, in poker, 3 of a kind beats 2 pairs.
Yes, in poker, 3 of a kind beats 2 pair.
Yes, in poker, a 3 of a kind beats 2 pairs.
No, Three of a kind can not beat a straight.
Yes, in poker, a straight beats a three of a kind.
Yes, in poker, a full house beats a three of a kind.
No, in Texas Hold'em, a 3 of a kind hand beats a 2 pairs hand.
Not in 7 card poker.