5. Is there a ban on donations from Trade Unions to political parties?

The Australian Electoral Commission is required to establish and maintain a Transparency Register which lists donations to political parties by Associated  Entities which include Trade Unions.  

Sources : Section 287N (1),  Commonwealth Electoral Act, 1918. (Compilation 68).

Australian Electoral Commission Transparency Register for Associated Entities, see  https://transparency.aec.gov.au/AnnualAssociatedEntity