CUL

A: Yes, it will. If you install the supplied INF-File also Windows will recognize it ie. as a Modem.

A: The current versions hardware and antenna is tuned for 868 MHz. But users have reported sufficent reception even at 433 MHz. So its worth a try.
We might offer a 433MHz-hardware-version at a later point.

A: CUL itself is just a hardware. From a physical/hardware prospect it obviously will work.
There are people developing a dedicated CUL-firmware to support FS20 (and other devices from ELV vendor) within the open source FHEM-project.

A: We suggest to stick with the simple wire antenna. This should be sufficient in most of the cases.

A: The CC1101 transceiver supports both modulations. Its just up to its register settings to do the one or the other. In effect: You may even change it in operation.

A: Follow the easy steps described here: DFU Bootloader

A: If the bootloader is corrupted you will have two choices:

1. Sent the device back to us for service or:
2. Use the ISP adapter with an ISP programmer and physically re-flash the bootloader with AVR Studio.