To add on, one of the biggest challenges with a full flow staged combustion engine is that the exhaust gas from the oxidizer rich turbopump is almost pure gaseo

To add on, one of the biggest challenges with a full flow staged combustion engine is that the exhaust gas from the oxidizer rich turbopump is almost pure gaseous oxygen at very very high temperature. This combination likes to corrode and eat away any thing, metal included. To solve this, SpaceX had to develop special metal alloys that could withstand this incredibly corrosive environment for long durations.