Answer: UN Statistical Commission, working with other IGOs in the Inter-Secretariat Working Group on National Accounts (ISWGNA).
Answer: Typically you will find: SNA 2008 and ESA 2010.
Answer: Most countries report to ISIC Revision 4. Occasionally earlier revisions are still in use such as ISIC Revision 3 and ISIC Revision 3.1.
Answer: Mainly from the OECD but also from Eurostat, the EU statistical organisation.