Where should an object be placed in front of a convex lens so as to obtain its virtual, erect and magnified image?

If an object is placed at the focus of a convex lens, where is the image formed?

Where should an object be placed in order to use a convex lens as a magnifying glass?

Where an object should be placed in front of a convex lens so as to obtain its real, inverted and magnified image?

For what position of an object a real, diminished image is formed by a convex lens?