See the occupations listed under subclass 457 along with the caveats applicable to each occupation as on 01/07/201. Visit https://www.legislation.gov.au/Details/F2017L00848
An example of how caveat works:
Accountant (general) – The occupation is inapplicable:
The details of caveats that are applicable to the occupations are listed on: https://www.legislation.gov.au/Details/F2017L00848
Police checks have become mandatory for all 457 visa applications lodged on or after 1 July 2017.
English language requirements:
The exemption for applicants with a salary over AUD$96,400 has been removed for applications lodged on or after 1 July 2017.