>>57876591. I'm sure there are but I don't like dolls that small so I pay no attention.
2. They are hollow pieces held together with elastic. As a result they can be completely disassembled and restrung.
3. Resin which I would describe as a plastic that looks like porcelain but with none of the cons.
4. You get what you pay for mate. You can buy them as cheap as $120 USD but those are shitty dolls and even then they need eyes, wigs, painted makeup, shoes, clothes, accessories, etc etc etc. When I put money aside for a new complete doll I allot a minimum of $1000 AUD for everything. (Or I did before AUD tanked) It's a real slippery slope so don't get into dolls if you're pinching pennies.
I'm glad to see a newfriend, feel free to ask if you have any more questions. We also have a guide up top but I know it's more for people who already have a background knowledge of BJDs.