1. They don't need it, but depends on the chins, some like them some don't. Males also use them sometimes for humping too... Also if they are use to it already it can be comfort if something happens to one of them.
2. It's best to give a variety of hay, it keeps the hay interesting, as well as each type of hay is chewed differently. So each wear down teeth differently which can help prevent tooth spurs.
3. Apple (or any other kind of chin safe wood) sticks can be given unlimited, so you can give as many as you can afford to give a week. My guys normally get about half a dozen of various kinds of wood chew sticks a day.
The most common and easy to get hay include, orchard, botanical, and meadow, which you can find at pet stores, but any grass hay is good. You can also give grain hay, like oat hay, but only as a treat hay, about a handful worth a week.
The timothy should be the primary hay, so no more then 50/50 mix. I have 3 hay feeders for my two chins, if I fill all three I do two with timothy one with other hay, or if I just fill two I do one with timothy the other with something else. I also buy a big bag of timothy and then one smaller bag of something else, getting something different each time.
The timothy hay I get comes in a box that allows the hay to breathe and protects it from any sunlight. However, I'm thinking about purchasing the second hay from a different company and it isn't in a breathable box, just a bag. How would I store that hay?