no
no
yes a BDL rifle will fit a ADL stock but the trigger guard will not but a new trigger guard can be bought for 20 to 50 dollars and brownells.com
700 ADL Long Action
NO
Yes they are interchangable.
Probably not but call your local gunsmith
No, the Remington Model 1100 stock has a hole (recepticle) through the inside of the stock in the pistol grip area to accept the action spring tube. The Remington Model 870 stock has no need for this hole so the 870 stock will not fit on the Model 1100 action.
no there are some minor adjustments to the safety area
No
Sorry, no answer from me, but I would like to know the answer to this question as well.
You have answered your own question.