Like almonds and hard candy. Porcelain veneers harder than enamel?

Not really. It's possible that they're harder but they're more brittle than enamel. When biting down on hard candies you are more likely to crack a porcelain veneer than an intact tooth.
Maybe. If you have damaged your own teeth you need to solve that problem before adding porcelain veneers. They are very strong but so is enamel make sure if you have a habit or movement that has damaged your teeth that it is addressed before starting.
Yes. Todays porcelain veneers are harder than natural tooth structure but they are not indestructible. They can tolerate normal day to day function but should never be used like tools. Bad habits like opening bags, biting pens or biting fingernails can destroy anything in your mouth. Shelled almonds are ok, hard; biting hard candy a big no-no. You would never punch a brick wall.
No. Enamel is still harder to break than porcelain. Zirconia is a material that is harder than porcelain and used to store teeth but nothing beats healthy enamel against almonds and candy.
No. Unless you have an artificial metal joint or titanium dental implant there is nothing in your body harder than enamel -- not even bone. Porcelain veneers are usually very thin and are quite fragile until bended to the tooth. They are then quite strong. However, they are still glass and glass can break. You should wear a nightguard and avoid crunching / biting very hard things with them.