Probability of Yahtzee game

#1
Hi, i am new to this forum. Sorry if i post in wrong place.

Have anyone played Yahtzee game?
It's a popular game with 5 dice and you can roll up to 3 times: http://boardgamegeek.com/boardgame/2243/yahtzee

My question relate to this game. Assume that you have 5 dice, in turn you can roll, keep and re-roll any dice up to 3 times.

What is probability in 3 times roll to get:

Specific "2 of a kind": 1-1, 2-2, 3-3, 4-4, 5-5, 6-6.
Specific "3 of a kind":1-1-1, 2-2-2, 3-3-3, 4-4-4, 5-5-5, 6-6-6.
Specific "4 of a kind":1-1-1-1, 2-2-2-2, 3-3-3-3, 4-4-4-4, 5-5-5-5, 6-6-6-6.
Specific "3 in a row": 1-2-3, 2-3-4, 3-4-5, 4-5-6.
Specific "4 in a row":1-2-3-4, 2-3-4-5, 3-4-5-6.
Specific "5 in a row":1-2-3-4-5, 2-3-4-5-6.
Total above or equal 15.
Total above or equal 20.
Total above or equal 25.
Any two different pairs (ex,2-2 and 3-3).
Any full house (ex, 2-2-2-3-3).
Any three of a kind (ex, 4-4-4).
Any four of a kind (ex, 5-5-5-5).
Any small straight (ex, 1-2-3-4).
Any large Straight (ex, 1-2-3-4-5).

Thank you, :)
 
#3
It depends on your strategy of how you choose which die to keep.
Is there any way to calculate general Probability?
Example, 1-2-3 always easier to roll than 1-2-3-4, regardless strategy right?

Can you help me count probability in all (or some) strategies?
I am designing a game so this is very important to balance the game.
I will very grateful for this.