Tastes like vinegar.
It’s fortified wine, so it may be OK if the bottle and cork are in good condition.
Probably not. Perhaps even decent, depending upon how well it was made.
Vintage Madeira
"...And their long lives have made them absolutely unique in the world of wine. Most wines are dead and gone at age 100; and at best they are barely drinkable. But after a century, a Madeira can be just reaching its prime, possessing the depth of great age, but also the vigor of youth."
An amazing find though!