I think that @Cameratose is correct. Parameters you set for Auto ISO are only available in regular modes. Full Auto sets everything for you. That's why it's called Full Auto. I don't think I have ever used a Full Auto setting on any camera I have ever owned because you don't have any control at all.

Are you using the timer to take the shots? Have you looked at the online guide for your camera? I would think that if you short press the shutter button you would have to do it three times - one for each shot.

You can set the max ISO in auto mode in the settings. https://helpguide.sony.net/ilc/1930/v1/en/contents/TP0002727476.html