GooglyBoogly
Freakamongus
1) Yes, but only if the grenadier attacks - as the bonus applies only when grenadiers Attack riflemen, and not the other way around.
2) The game engine chooses the unit with the greatest odds of victory, this is not always a good thing in some situatons, most notably fights that involve the single medic promoted unit being chosen to defend over any of its wounded bretheren, and thus if it dies your units will heal MUCH less since there is no more medic - in a similar vein you may find that your Great General attached unit will defend when you would rather that a lesser unit were sacrificed. The game engine also does not take into account unused promotions, so you may lose a 5xp spearman over a 0xp one just because of their ordering (since they would have the same strength)
2) The game engine chooses the unit with the greatest odds of victory, this is not always a good thing in some situatons, most notably fights that involve the single medic promoted unit being chosen to defend over any of its wounded bretheren, and thus if it dies your units will heal MUCH less since there is no more medic - in a similar vein you may find that your Great General attached unit will defend when you would rather that a lesser unit were sacrificed. The game engine also does not take into account unused promotions, so you may lose a 5xp spearman over a 0xp one just because of their ordering (since they would have the same strength)