I’ve flashed new builds and I’ve replaced FC and flashed FC with what the original had on it but this is the first time I’ve updated a FC with the quad setup how I like it.
 I did a diff all and saved to a file so if updating goes bonkers I can go back.

  I found a JB video and he starts completely over but it was an update to the first 4.2 version of betaflight.
 I have 4.2.5 but was going to update to 4.2.9 or latest version.

 How to I update betaflight and not lose settings?
 Also is there any reason why JB started completely over like it was a new build when going to 4.2 for the first time?

Yes. Any settings in Betaflight 4.2.5 are 100% compatible with any other 4.2.x version. So save a "diff all" of your current Betaflight 4.2.5 settings, upgrade the FC to Betaflight 4.2.9 and then restore the original Betaflight 4.2.5 settings by pasting (or loading) the "diff all" you saved into the CLI.

(07-Sep-2021, 05:46 PM)SnowLeopardFPV Wrote: Yes. Any settings in Betaflight 4.2.5 are 100% compatible with any other 4.2.x version. So save a "diff all" of your current Betaflight 4.2.5 settings, upgrade the FC to Betaflight 4.2.9 and then restore the original Betaflight 4.2.5 settings by pasting (or loading) the "diff all" you saved into the CLI.

  That actually makes sense.
 I finally understand what a “diff all “ file should have in it.

Just a side note to add. After flashing the FC, you still need to click the "Apply Custom Defaults" button when first connecting to the FC. This ensures that the base configuration for the FC gets applied before you restore any of the "diff all" settings.

(08-Sep-2021, 07:11 AM)SnowLeopardFPV Wrote: Just a side note to add. After flashing the FC, you still need to click the "Apply Custom Defaults" button when first connecting to the FC. This ensures that the base configuration for the FC gets applied before you restore any of the "diff all" settings.

  The accelerometer was out of calibration but the after “diff all “ restoration it seems to be calibrated.

  I seen accelerometer settings in diff all files so it doesn’t need recalibrated?

(08-Sep-2021, 04:31 PM)Rob3ddd Wrote:   The accelerometer was out of calibration but the after “diff all “ restoration it seems to be calibrated.

  I seen accelerometer settings in diff all files so it doesn’t need recalibrated?

No, you don't need to re-calibrate. if the accelerometer was calibrated correctly before you re-flashed new firmware then restoring the "diff all" will also restore the prior (correct) accelerometer calibration.