Among the following options, the CORRECT one is
1. Rhombus is a cyclic quadrilateral
2. Diagonals of a rhombus are equal
3. A rhombus that can be inscribed in a circle is a square
4. Opposite angles in a rhombus are equal

Rhombus is not a cyclic quadrilateral as the sum of opposite angles is not always 180 degrees.

Diagonals of a rhombus are not equal except in the case of a square.

A rhombus which is inscribed in a circle is always a square as it will be a cyclic quadrilateral for which the sum of opposite angles must be 180 degrees which is possible only when it is a square.

The opposite angles of a rhombus are equal.