Whiskey Go Bad

Can rum go bad if its been opened but the lid is on?10 POINTS?

I found an old bottle of european 80% rum or whiskey the lids been opened before but i dont know how long ago and the lid has remained on and I think it could be up to 20 years old
could it have become stronger and increased in alchohol content?

Generally put, things like rum and whiskey (and any hard liquor) is going to taste the same no matter how long it has been in the bottle. It doesn't go bad, but once it has been taken out of the barrels and bottled, it is not going to increase in alcohol content. That is the difference between fermented and distilled drinks. Beer will go bad eventually even in sealed bottles or cans. Depending on what kind of wine it is, it will either age to perfection or age to vinegar. But rum or whiskey will stay more or less exactly the same in the bottle.

The only hard spirits you have to worry about age are the ones that are premixed (especially ones that have cream or milk products like mudslides). Those need to pretty much be refrigerated and consumed in a reasonable period.

sunfish - Mola Mola - whiskey don't go bad