Earned premium is that portion of the policy coverage has been extended. For example, if has been 2 months since you started the policy, 2 months of that policy has been earned.

Yes. Insurance companies agree to cover the events listed in their auto policy for an agreed upon premium. If you stop paying the premium, they'll stop providing coverage. If the company has extended coverage on your behalf, you could still owe them money for "premium earned" after cancelling it.

They are required to refund any unearned premium portion. Policy fees and the like are considered fully earned.

Excess of loss reinsurance coverage typically has no direct effect on unearned premium. Unearned premium represents the portion of an insurance policy premium that has been paid in advance but has not yet been "earned" by the insurer due to the coverage period still being in progress. Excess of loss reinsurance helps protect the insurer from catastrophic losses by providing additional coverage, but it does not impact the timing or calculation of unearned premium.