ECU Learning reset.
 

So the ECU learns to some extent over time. If I want to undo what has been learnt, what is the best method.
1 Reload the OFT tune.
2 Disconnect the battery.
3 Do a ECU reset(Clear with scantool)
I`m just curious which is the best

they achive the same, just delete dtc as it s simpler
Ecu learns fuel trims mostly and keeps Memory of AM if it drops

All options are valid, but option 2 is the safest.
With option 1 you always have a (very small) chance of bricking the ECU or writing an incorrect rom.