Concrete overlay are not recommended. If concrete is broken that means there is a problem underneath, For a proper job, removal of broken slab and base compacted are necessary, then a new concrete can be made.
It depends. If it is normal concrete cracks, say less in width than a thickness of a quarter, then yes. If there is any deflection in the concrete, areas raised, etc., then no. Pitted concrete can be made to look new with an overlay.
Today’s concrete overlay products are designed strong and durable. They can last for years and give your concrete a brand new look.
Concrete overlays in some situations make sense. For example if you need to resurface around a pool and have expensive landscaping and no way to use heavy equipment to demolish. The most important thing to remember is the overlay is only as good as what’s underneath it. If the concrete is breaking down and crumbly the overlay will just come up with the existing concrete.