You must have physically met your sponsor in person (as adults). You must be known to the person that you intend to marry, even if it is an arranged marriage.

If you and your sponsor marry before a decision is made on your Prospective Marriage visa, you can change your application to that of a Spouse visa at no extra charge. You must provide a certified copy of the extract from the marriage register showing your marriage to the office of the department processing your application, write that you wish to change your application to that of a Spouse visa and that you formally withdraw the Prospective Marriage visa application.

You visa would have been granted on the basis that you were assessed as genuinely intending to marry your sponsor. If you do not abide by the conditions of your visa it may be canceled and you will have to leave Australia. If you marry a person other than your sponsor, you may still be able to lodge an application for a Spouse visa in Australia. However, in many cases, if you do not marry your sponsor or if you marry another person instead, your visa may be canceled and you could be required to leave Australia.

No. However, you must make at least one entry to Australia on the Prospective Marriage visa before you marry to fulfill the conditions of your visa. If you do not, you may not be allowed to enter Australia and your visa may be canceled. If you marry outside Australia, this must be a marriage that is recognized in Australia for the purposes of the Australian Marriage Act 1961.