EBay doesn't provide any products they only provide a place for people to sell their items. They don't help you either they just collect the money. So it's like if you hire a stall at the markets to sell your household items. The person you hire the stall off has nothing to do with the items you sell nor would they guarantee the items, they just collect the money for letting you use their stall. People need to understand eBay sux and just rips you off! For example you sell something for $200 you pay $24 in fees and listings. Sell that same item 3 more times and that's $100 in fees

This depends on the seller of the item - carefully check their feedback and trust you intuition if you have doubts try another seller you feel safer with...

New things are mainly chinese craps with false specs, you can find these craps in the chinese shops in your town
Used things maybe obviously good and not good, as the things you can buy in a local charity