StringBuilder is more efficient in cases where there is a large amount of string manipulation.  Strings are immutable, so each time a string is changed,
a new instance in memory is created.

No

The Clone() method returns a new array (a shallow copy) object containing all
the elements in the original array. The CopyTo() method copies the elements
into another existing array.Both perform a shallow copy.
A shallow copy means the contents (each array element) contains references
to the same object as the elements in the original array. A deep copy
(which neither of these methods performs) would create a new instance
of each element's object, resulting in a different, yet identacle object.

By calling Sort() and then Reverse() methods

HashTable.

A sorted HashTable.

Yes.

A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch { }.

No.Once the proper catch block processed, control is transferred
to the finally block (if there are any).