1. Because they want to land the Lander also (The lander itself have many Scientific Instruments too), If they can land 2 (Lander and Rover) in one Go, why need 2 different landing approach?
2. 90 days is minimum target of Operation, as long as the Rover alive it will be keep roving in Mars to the distant future. It Fully Solar Powered. Just like their Yutu 2 Rover on the Far-side of the moon, programmed only 90 days, but still alive and roving across the moon until this date.
3. Both
I need to remind you, your indian logic cannot match The Technology that China have today. That's why you confuse and accusing them failure
@dbc