Well.. I think the title of the topic is clear enough... When playing attachments which can be attached only on heroes belonging to a specific sphere, (such as "a burning brand", or "Support of the eagles") I guess they can be played on Gandalf as they are played from the top of library. I am right ? Because while, playing them, Gandalf has de matching sphere.

The second issue is. When Gandalf loses the sphere... the attachment stays, or it is discarded ?

i think Gandalf can attach Burning Brand when he uses his ability. And it is forever. IMO

They can be attached and ye does not lose them after attached wher resource icon goes away.