There is sooo much of this on EOS that it can be confusing!
Here is a link to the Horizontal Property Act (In English), that's a good place to start.
First off:
"What I have read there refers to Horizontal Property Law but also states that we all have to contribute to maintenance of the properties (terraced back to back townhouses)."
Yes! Every owner pays 'Community Fees' which contribute towards many things including maintenance of the community.
And in answer to your questions:
1) Yes! Your administrator will have a copy.
2) No! To change anything with regards to how the community is run, then the request must be presented at an AGM or EGM and it must be included in the Agenda prior to the convening of the AGM/EGM. Then a vote will take place during the AGM or EGM. If it's not in the Agenda, then it cannot be voted on during that meeting, and must be proposed and voted on to include during the next meeting.
During the AGM or EGM, you only need 51% of the quorum (those officially attending or officially represented via proxy) in order to make the necessary change take effect. Note that anyone in arrears of the community fees will not be allowed to vote, however can attend the meeting.
3. As far as I am aware, the duties of the community officers can be supplemented by such that is agreed via vote at and AGM or EGM.
Lastly, having quarterly reporting on the state of finances and want it written in to the constitution is a waste of time.
A simple quarterly News Letter stating 'What's going on in our Urb.' is all that's required to keep 'bothersome' owners happy. If they wish to know the state of the finances then they can simply contact your administrators and get all the info they need from them!