Australian English: developed or developped?

Solution 1:

While I do not know how normative it is considered in Australia, the Macquarie Dictionary refers to itself as "Australia's National Dictionary" on the cover. I have a slightly older printed version, but it is also available online for paying subscribers.

Macquarie Dictionary, Revised Third Edition (The Macquarie Library, 2003):
developed /də'vɛləpt/ adjective 1. having undergone development. 2. industrialised.
developing /də'vɛləpɪŋ/ adjective 1. undergoing development 2. Also, less-developed, underdeveloped (of a country) in the early stages of developing an industrial economy.

Solution 2:

The OED recognises developped and developping as past tense/participle and present participle, but states that both have been "non-standard" since the eighteenth century.

The OED recognises a corpus of English around the world and were they in current Australian use, I am sure would say so.