Report An Issue is intended for Reporting Possible Software bugs. Questions on how to work with FileMaker Pro should be posted in the FM Pro Forum Section. (See tab at top of this screen.) (I'm telling you this because you'll get such questions answered much more quickly, on average and they'll be seen by many more fellow developers if you post your question in the correct location.)
1) You do not have to make any layouts customized for use with the iPad, but it's a very good idea. The iPad's screen is much smaller than that of a typical computer screen so what works well for a layout design for a computer may not work on the iPad without being quite awkward to use. Also. a mouse is a much more precise pointing device than the blunt tip of a finger so controls that are easy to use with a mouse may be difficult to use with a touch interface. The "Touch" themes aren't required, but they are set up to use larger sizes for layout objects to better work with a touch interface design.
In addition, since more iOS applications will modify their screens to better use the available space when the device is rotated, you may want to design layouts--possibly with scripting using the onLayoutSizeChange trigger to change when the device is rotated. (Or you can use auto-size anchors to create a layout that modifies to fit the rotated device screen.)
You may find a few of the techniques in this thread on designing layouts for FM GO helpful: An Old Dog learns some new tricks...
2) You appear to be confused by what is meant by "flat file". By definition, a flat file database would consist of a single table and no relationships linking it to other tables. But the best design for your project will depend on what you want it to do. My best guess is that you won't get the best possible results with a flat file design, but will need to use multiple tables linked in relationships.
3) It is possible to take a picture from the iOS device's camera and insert the image directly into the container field of the current record. Look up the Insert From Device script step in FileMaker help to learn more about your options.
There is a section of this forum specifically set up for FM GO users. It is probably the best place to post your questions about FileMaker on an iPad here in this forum.
Thank you for your answers. I will check the Filemaker Go forum.