No, they are 2 totally different bodystyles
no.
1989-1994 should fit.
Any steering column from a 1986-91 Eldorado would work - a comparable Seville's should work equally as well.
1988 to 1991 most parts are interchangeable - body styles an other things changed after 1991
Yes
Yes
yes?
YES
Yes, most parts should.
Depends on what parts you're referring to, but most parts would be interchangeable
Some parts are interchangeable, depends specificallyon what parts you're referring to
Yes