Hi,
Below is the answer.
1) Yes, as different model might have different requirement and features needed. It will more important if you would like to have it fully run in FPGA.
2) You may refer to https://docs.openvino.ai/archive/2019_R1/_docs_IE_DG_supported_plugins_FPGA.html where it will provide the information on what is the supported model for that bitstream. If not you will need to ask Terassic on the bitstream as it is providedby them
3) If all the features is supported on the bitstream then you can run with "-d FPGA". If the features is not supported then it will not break away but will mention that it is not able to run with "-d FPGA".
4) Yes, you are correct. For the Terassic board then you will need to contact them on the bitstream available as it is not part of the OpenVINO installation package.
5) You will need to contact Terassic if you are interested on the building custom bitstream for their board. If not you will need to contact your local sales person for Intel AI Suite(https://www.intel.com/content/www/us/en/software/programmable/fpga-ai-suite/overview.html).