You can downgrade the firmware, but to do so you need to ask SharkRF for the version you want by email, email@example.com will get to them. To downgrade you need to get into bootloader mode and then copy the supplied file to the bootloader drive. To be honest I have never needed to downgrade a beta firmware, they are of good quality and often get upgraded to a release without any changes.
The modem is the RF modem that your transceiver transmits to and receives from, it uses an ADF7021 chip which can operate in different modes depending on your transceiver. The connector is how the openSPOT talks to the server you have selected, it changes the protocol that is sent to the internet/server via the WiFi connection from the openSPOT into whatever device gives you your internet connection.
To crossmode you keep the modem set for your transceiver and then change the connector for the server you want, you can save specific settings into a profile which can then be changed via the web interface or via your transceiver. As you note this reboots the openSPOT (this is necessary) when a profile is changed.
I can't help much with your iPhone problem except to say that iPhone hotspot use can be problematic because it's how Apple have decided to design the setup.