6. Is there a ban on donations from Trade Unions to candidates?

Commonwealth Electoral Act 1918 s 287N. Australian Electoral Commission Transparency Register for Associated Entities, see https://transparency.aec.gov.au/AnnualAssociatedEntity

The Commonwealth funding and disclosure scheme detailed under Part XX of the Commonwealth Electoral Act 1918 (Electoral Act) requires associated entities, which include trade unions, to lodge annual returns. The Commission Transparency Register of associated entity returns shows the funds provided by trade unions to political parties.