USB stick to iOS device operate?

1. There's indeed the camera adapter with Lightning plug and USB socket, via which you can copy, for example, photos / videos directly from the stick to the iOS device.

2. Then there are memory sticks that have both a Lightning and a USB connector. These can be used like any normal USB stick on the Windows laptop. In addition, you can plug it through the Lightning connector directly into the iOS device. Using the app of the stick manufacturer, you can then manage all sorts of file types, not just photos / videos.

Now for my concern:

Can I insert a "normal" USB flash drive (without Lightning) into the adapter (1.) and access it with a file management app (2.) or can these apps only come with sticks that are from the same manufacturer, like herself?

Microsoft and Apple do not like each other.

Nee is just not why.

Only goes for pictures

It should work with an adapter. However, I'm not sure how "data management apps" support the whole. From iOS13, which appears in the fall, supports iOS but natively USB sticks.

It can be operated so far no USB stick natively by adapter to an iOS device, because simply the corresponding power supply is missing, technically possible, but not available in the system.

The memory sticks mentioned under (2) are not flash memories but with a special power supply that still does not allow full file access from iOS.

From iOS 13 / iPadOS, available from autumn, USB sticks are natively supported. Wait a few more weeks.