The short answer is no - proper inverter matching is crucial for optimal performance and safety. Let's examine the key compatibility factors for lithium battery and LiFePO4 battery systems. Lithium batteries require specific inverter features: Voltage Matching.
A white surface will scatter the light, and unless its really close to the target, not much will reach the solar panel but diffuse away in all directions. You could just try reflecting the sun's image onto a nearby wall. First with a mirror, and then with a white surface.
Two common DIY methods for repairing cracked solar panels are covering the panel with a laminating film and applying polyurethane. The laminating film method involves spreading a transparent, waterproof film over the cracked panel and using a heat gun to fuse it to the surface.