Is there anyway to bypass this, how could I scan the entire A4 photo at 4800 dpi?
You cannot bypass the limitation. As Zeiss Ikon states, you can scan several pieces and stitch. However, my personal attempts at doing so have been disappointing in terms of both wasted time and image quality (stitching artifacts).
… would it not be a software restriction rather hardware related?
Your scanner has a Contact Image Sensor (CIS). The sensels run the width of the scanning area and are positioned close to the surface they are intended to scan. To achieve 4800 DPI, a portion of the sensor likely has a higher density of sensels. There would be no way to scan at 4800 DPI outside of that area.
Other scanner technology use lenses and small, linear sensors. The sensors have fixed size and sensel density. To achieve higher DPI, the scan area has to be reduced because the sensor cannot be changed.
Many scanners allow higher resolution settings than the hardware is actually capable of providing. This is done via interpolation. If such solutions are sufficient for your needs, you can achieve the same results by resizing lower DPI scans in any image editor.
Most prints do not provide detail beyond ~300-600 DPI. Since you are scanning toy boxes, most of what you would be capturing is the halftone pattern.