Warning light / reset / engine RPM issues

We've had our 2006 Corolla Verso 1.8 petrol for 2-years without any issues until the other week when the general engine fault light and 'TRC OFF' and VSC lights all came on while driving - at the time the car was 10-minutes into a journey from cold. With the lights on I didn't note any difference in performance.

As I had no code reader at the time I wanted to know if it was a permanent fault so I disconnected the battery and reconnected it, this cleared the fault indications. Since then no fault indications came back, done a few hundred miles since.

I did a few test drives immediately after the reset and everything was generally okay apart from:
  • Once it appeared to stall while on the move - I put my foot on the clutch, lots of lights came up on the dash and then the engine revs picked up to idle like it had re-started itself? (this happened very quickly, but I definitely didn't press the start button!).
  • Sometimes at idle the engine RPM dipped slowly over around 5-10 seconds to a stall speed before picking up again to normal idle - this then repeated over and over when at idle on a number of occasions.
I have since bought a code reader but there are no active or stored codes - I guess I cleared even stored codes by disconnecting the battery!

Playing around with code reader and viewing live engine data I have taken some logs but haven't gained much from these as I have nothing to compare them to! I did however see some VERY high spikes in the recorded engine RPM in the data - e.g. up to over 12,800 RPM! These spikes in the data only occurred after I revved the engine lightly from idle and then took my foot off the throttle - the spikes occurred as the engine rpm was dropping back to idle - I'll attach a photo of this below (the engine RPM did not increase at the time of the spikes!)

From the above I have a few questions..!

  1. I guess there's no knowing what the fault was, but should disconnecting the battery clear all stored faults, or was this because I left it too long?

  2. Any ideas why the engine revs would drop to a stall speed several times? Could this be due to it re-learning post the power-reset?

  3. Can the engine actually restart automatically while you are moving if it does stall and you have the clutch down? Or did I imagine this!?

  4. In relation to the RPM spikes - has anyone seen this kind of thing before? I used the Torque lite and Torque app's with a torque pro ELM 237 reader which seems pretty standard stuff in use.

Any help on any of the above would be appreciated!