Chipboard should ideally be laid flat and level before any hardwood flooring is fitted. Do not use an underlay to level a subfloor.
Chipboard is not waterproof. There is a moisture-resistant variant but it still swells if left wet for too long.
Laminated chipboard is stronger and smoother.
Chipboard is the cheapest and weakest of all materials so it's not a great choice for shelving.
No, the chipboard is vulnerable to moisture and will absorb all the moisture and swell.
Chipboard absorbs any moisture in the air so it will swell and become unusable.