Most of the answers you will find in the Horizontal Law, an English translation can be found here: http://www.eyeonspain.com/spain-magazine/horizontal-laws.pdf
1. It's the master deed, or estatutos; have a look at Sections 5 & 6
2. Section 10; the community should have building insurance of course, and depending on how old the property is, the builder may be responsible (and should be covered by insurance)
3. Again, section 10 and the definition of each property as described in the deeds
4. If a majority vote has been taken and recorded according to the rules set out in the HL, to increase the budget, meaning each individual owner must pay more, then any owner refusing to pay the new amounts would become themselves a debtor, and lose their right to vote. Of course, the quotas for the original non-payers would have to be increased accordingly too, so when the money is finally recovered, the imbalance should be corrected. Does that make sense? (It's late!)
Hope this helps a bit.
P.S. I'm no expert on these matters - watch & hope for a reply from Maria, her opinions / advice are more reliable.