Please don't use TIF files for images. This is not a good web image extension. This is very heavy image type and the memory of your server may not allow PHP to manipulate with this file and create a thumbnail. I think the problem in this file format. And PHP can't crop and re-size TIF images.
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Do you mean alt and title of the imported files?
If so I'm really sorry but there is no way to revert those back.
Why not, if they all will disappear later?
I'm sorry but I didn't follow you. What attachments you mean and why they should disappear later? If something exists now it'll never disappear.
wpForo Advanced Attachment doesn't have image description feature. You can check it here.