Yes.
Yes the interception would stand, but no, there wouldn't have been a penalty.
The penalty for an Illegal Forward pass is a five yard spot foul and loss of down. If an Illegal forward pass is intercepted, the penalty would be declined. There would be no enforcement of the penalty.
yes as long as it gets caught. you can throw a pass that is a loss of 30, it's still a completed pass.
yes it is considered a penalty.
Yes it is income, plus you will be assessed a penalty.
James Farrior of the Steelers was offside on the third play of the Packers first possession in the first period but the penalty was declined. The first accepted penalty was a block in the back on a punt return later in the first period by Ryan Mundy of the Steelers.
yes
The only time the offense would decline that penalty, would be if the resulting play advanced them more than 15 yards down the field. Either way, they would have a first down.
There is an early withdrawal penalty of 10% of the amount you withdrew. Keep in mind that this penalty is in ADDITION to the fact that in most cases the withdrawal will also be counted as taxable income. So you will pay income tax on it AND a 10% penalty.
yes but the game can only end on a defensive penalty if it is declined by the offensive team
it would take place at the line of scrimmage and the team that is not guilts of offsides will get the option to accept or decline the penalty, if declined, the play stands as called, if accepted, the play would be redone 5 yards deeper