Have you tried out any Android devices, yet? Normally this should work with iOS as well. However, we do not have an iPhone 4 here to test this. I will check the functionality with iOS again tomorrow.
For now, you can also go the old-fashioned route of our classic tutorial for the Access Point: https://www.instructables.com/id/Raspberry-Pi-Mobile-Media-Center-with-Smartphone-C/
You just need to first connect it via LAN to set up the access point.