1- If I received an invitation on 491, when i can get married!!? After receiving grant or after first landing!??

2- is that right to make first landing only 4 days and back again to get married !??

3- And what is the period allowed to stay out of Australia after first landing!??

4- if i'm from Egypt an work at Saudi Arabia, can I make first landing for 4 days then go back to Egypt to get marry then go to my work in Saudi Arabia for 2 or 3 months then back again to Australia!??