- have an app called astronomy that does not exist anywhere else on the device, never seen or heard of it before.
As Zachy said that is not an app and is a wallpaper and does use cellular data. Nothing to be concerned about, it's the one with the planets.
-check cellular under apps, only maybe a third of them actually show data used, totaling nowhere near what’s been displayed as used.
Never seen the totals match by adding up the listed apps myself either, but I also do not regularly reset my statistics to troubleshoot, and have not seen where Apple documents additional usage that does not fit nicely in an app category. Certainly cellular data is being used for other uses that are not noted with apps or even many of the System Services categories. You can check in the Support Article here and see that example screenshot does not even come close to matching app usage, even though all the apps are not listed. You also have the iCloud Drive and iCloud Backup switches you can turn off. If you want to contact Apple directly, you can also do that to see if you get an explanation. It has been reported many times here, but I have not seen where anyone has followed up by contacting Apple and provided an update.
Use cellular data on your iPhone or iPad - Apple Support
Contact Apple Support - Apple Support
-have found unfamiliar apps in the past that would not allow me to delete them, could not be found in the App Store or come up when searched
What apps are you referring to. You can provide a screenshot if you wish. They should still be there if you were not allowed to delete them.
Not sure why no one responded to your previous post, the Astronomy one has been asked frequently and the answer is readily available. Posts are only removed when the violate the Terms of Use for the site. I did not see your previous post, so have not idea what the reason would be. As long as you stick to the technical support questions that the site is designed for, it should be no problem. Of course, this is not a Social Media site where rants are a common place, so those would most likely be dealt with appropriately like you would expect.