Is it easy to enable/disable the shift bypass or alter the F11 setting remotely? Yes, if you know how. If you don't it shouldn't take long to Google it and find the code.
This can be a good thing. You could put the db in a state where you cannot log in yourself due to a coding glitch, db setting, table data issues (wherein the table(s) are not split) or corruption. If you could 100% disable the bypass, you are toast if that happens. I use an "easter egg" to cycle the bypass property, changing a label background color to red so I know when it's enabled.
The topic of Access security is often a hot one. It is my opinion that the most ironclad Access database is still not as good as the least secure sql server product that doesn't use Access as a front end. A poster here once claimed to have an iron clad method, but he declined my offer to try to break it, so all I can say is I know of no 100% secure approach, (I have very little experience with Access Runtime versions so I don't know what degree of lockdown that provides). You can only make it more difficult for the less informed to tamper with as ItsMe said. For those who know enough to be dangerous, we make regular backups.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.