When do I need to tune ignition timing?

I'm a beginner in ecu tune and I have some questions.

When do I need to tune ignition timing?

1. Stock set to use 91RON from the factory and want to use 95 or more

- basically advance the timing?

2. Stock recommend to use premium fuel from the factory and want to downgrade to use 91RON

- basically retard the timing?

3. Stock 91 from factory and modified airfilter and full exhaust but still want to keep it 91 (retuned AFR & Air table for each cylinder)

- Can I leave it as is? Or even can I just advance it 2-3 degree because it gets to have more air and more fuel? (No dyno in this case)

Every engine combination is going to be potentially different, but as a general guide -

1/ yes.

2/ yes - but it depends on things like the dynamic compression ratio of the engine, it's chamber shape, etc. Some may be already running close to the limits.

3/ depends - the charge is denser, so will burn faster and need less advnce, but it may be colder which could allow a little more advance.