You apply for the 820/801 at the same time, you can't skip applying for 820. If you fulfill the requirements for a long term relationship (at least 3 years as defacto/married or 2 years with a child of the relationship) and have sufficient evidence covering the entire length of your defacto/married relationship (note that periods of dating do not count), the case officer may choose to grant the 801 immediately after 820 is granted.