No such product corresponds to given parameters.
Imagine what it would be like to buy your baby bed that would grow with him. No legs sticking out of the bed. Just one bed up to the age of majority. That's exactly what extendable beds offer. You can extend the length of bed as needed. You simply remove the rails. When selecting a design for your child, choose a extendable bed in neutral colors. Keep in mind that what your child like now is not going to make him happy in teenage.