Generally, no. Permitting offices these days use satellite imagery history to detect unauthorized renovations. Plus, neighbors tend to get nosy and intrusive about non compliant builds.

The absence of plans on file are irrelevant. If the work involves construction that is controlled by the building code and/or the zoning ordinances, you must apply for a building permit.

No, you can’t turn it into an Airbnb without a whole lot of permits and money. A shed is not legally habitable.

Don't ask too many questions, they may only allow you to sleep in the shed and on the porch.

(humor)

Are you sure those are the "Certificates of Occupancy" and not like the permits. Not sure how would one get a CoO for a shed... since those missing typically smoke detectors, or CO, insulation, drywall, plumbing, proper electrical.

Many people gotten CoO for their homes, basements, ADUs ... but a shed and a "porch roof"? It is maybe conceivable ... [not really sure how].

It varies from area to area. Here you can re-side, re-roof, replace windows and doors all without a permit. And you usually can get away with any change you can't see from the road without a permit (no comments please!). Lots of work trucks and nosy neighbors may lead to a permit.

C of O's are odd things when an addition or an out building is constructed because the main house does not lose its C of O when a permit is issued for the extraneous work.

At any rate, the absence of drawings on file at the building department doesn't change anything.

The county has a building permit systems. We had to get a permit to have our AC replaced.

Recently a house about 1 quarter mile up the street, put a large canopy that he can put 4 cars under in Front of His house. I called the county and they came out and inspected it and said no codes were broken. However they also said here was no building permit. They said I could file a complaint and he would have to get one.

I did not do anything as the only one that would of benefited would have been the county as they would get their permit fee.

If you wanted to build an addition onto an actual existing home which already had a certificate of occupancy, you would still need a building permit. (In most jurisdictions, anyway.) The good news is that it looks like you could live in your shed while building a house (with a building permit).