it would depend on the players you have at your disposal and their strengths, but as a basic answer to your questions
1- 3 attack duties, both wingers and your goal scoring striker. 3 defense duties, 2 cb's and 1 central midfielder. rest support to maintain a good balance in the side
2- midfield partnership, advanced playmaker support - will look to control the space between the strikers and the midfield aswell as keeping decent shape + Ball winning midfielder - will look to press opposing players all over the park and win the ball back.
3- I'd put fullbacks on automatic, this way should you be 2-0 up for example you may look to sit deep and defend your lead, this would change their roles to suit.
This is how my current team is set up after a couple seasons growing from relegation battlers to euro contenders.
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Now I have not tweaked any individual player instructions etc and am doing reasonably well i think. Obviously there are tweaks that can be made to perfect this, such as has been made in modern warfare etc