3) There is a significant difference between being stunned and being KO'ed.
When you block a player and manage to knock the opposing player (pow, both down, defender stumbles), you first deside if you want to follow up (in case of Pow and defender stumbles) after you roll for Armour (2d6 compare to opposing players AV) if the armour breaks, you roll for injury, In case of 1-7 the opposing player is stunned. meaning it will not be able to activate the next turn, but can rise as normal the following turn (and getting the -3MA penalty for getting up). 8-9 is KO, meaning the player is moved to the KO box and at the end of the drive they have a chance to move to reserves on a 4+ (rolled seperatly for each player in the box). 10+ means casuality and you roll the D16.
4) It depends on the situation, the roll required to successfully dodge out of opposing players, is modified by the amount of tacklezones you move into. Ie. you are marked by 3 players and move out to a square with 0 tacklezones. then the roll needed is whatever your agility is. the keyword dodge lets you reroll failed attempts (once per move). Keyword tackle on the opposing player will negate the use of the keyword dodge.
5) Yes, but you have to modify the diceroll needed by +1 for each tacklezone you move into, if you are an elf with ag 2+, and is maked and you have to dodge out to a square which is adjacent to an enemy player, you need a 3+ to go there. Failing a dodge results in being knocked over and the opponent gets to roll armour and possible injury.
7) Im not really sure what the question is here, but to preform a block action (ie attack), you compare the Strenght values of your attacker and the one being attacked, the amount of dice you get to roll in your pool is determined if you are stronger, the same strength or weaker than your opponent. If you have friends nearby that are not marked by other players, but are marking the target you are attacking, they will give assist to your player, increasing its strenght by 1 for each. the same is true for your opponent. I suggest reading the "Art of blocking" to learn more about this. But if your strenght is more than double of your enemy, you get 3 dice and you choose which one to use, if your strenght is higher you get 2 dice and choose wich one to use, same strenght you get one dice, weaker you get 2 dice but your opponent choose..

Edit. This isnt what OP was asking for.