With an OBD2 scanner.
It's probably misfiring. You would need to diagnose why.
Either have the problem that is causing the light to illuminate fixed or disconnect and reconnect your battery.
It depends on the failure. It could be on immediately or it could take days.
dash dash
Have vehicle scanned to determine the problem
The easiest way is to unhook the battery for a minute.
have vehicle scanned to determine problem
By bringing it to a trained mechanic so they can check the engine is running properly (which if the light is on it's probably not)
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
Inside the engine compartment by the passenger strut tower
You either need a scan tool, or unhook the battery for a minute.
None. Engine timing is set by the PCM, you can not change it with a timing light.