(A) any magnetic metal is fine as long as the magnets can attract it, most common would be iron

(B) Consider what will happen when the battery is flat: the electromagnet can no longer attract.

Since there’s no more electromagnet attraction pulling the globe up, it will just be attracted to the permanent magnet only and fall.

(C) for the globe to float lower, the permanent magnet must pull harder than the electromagnet, therefore the aim is to weaken the electromagnet

Any 2 ways that weaken an electromagnet will work. Such as lesser batteries, reducing the number of wire coils around the steel rod etc.