which file format to use for the ios app tutorial which should be embedded inside the app?
The videos I've delivered for iOS App Previews have been as per the specification in this section, viz. H.264 video codec, Baseline profile, 30 fps, AAC-LC audio codec, sampling rate 48 kHz, stereo in MP4 or MOV. Resolution and bitrate haven't been restricted to what the docs say. Those should be tailored to the device(s) your app is for.