ISBNs and edition names

[Pinar]

1. Is it possible for two books which are published by different publishers in different years to have the same ISBN? I have come up with this several times here. I have the book, I search for it by name, I look at the editions, when I see they're not my edition I create a new entry. When I add the ISBN, the database tells me there is another book with the same ISBN. I look at the book and it's completely different from mine but it has the same same ISBN. Is it a wrongly entered information or is it possible?

2. These books, http://www.goodreads.com/book/show/64... and http://www.goodreads.com/book/show/64... are the same, however their title is wrong in both. One of them only appears in Google Books, and the other in amazon.in . Would it be ok to correct the title (I have another edition of them, so I know it)? Another example is this: http://www.goodreads.com/book/show/64...

3. Can this exist: Same ISBN number, same book, but different covers. Here, http://www.goodreads.com/book/show/81... and http://www.goodreads.com/book/show/82... are both the books I have with the exact same ISBN, however my covers are different. Should I add my covers as additional images? I don't think they are different editions, since I searched by ISBN.

I hope what I'm asking makes sense. Sometimes things get lost in translation :)

[Krazykiwi]

1. Yes, but it's an accident. It's not supposed to happen, but it does. Put a note on the one you're adding with the ISBN and what it's a dupe of (and maybe a note on the other one, so people looking up by ISBN can find the right book)
2. Yes, they should be corrected and combined
3. Yes, that is what alternate cover editions most often are. Add the book again, without the ISBN, give it the new cover and a librarian note saying it's an alternate cover edition of ISBN NNNN (and combine with the rest of them)

[Pinar]

Great, thank you very much!