Thank you for help, again I want to know after we submit the project, we can get the nucleo board, and the user area chip we design. How the chip we design connect to the nucleo board? is the chip already put on the nucleo board or there are another board hold the chip?

There is actually a stack of three boards. The Nucleo board is on the bottom. On top of that is a development board for Caravel with a socket (currently a set of Flexy-pins, but this is going to be replaced with an M2 socket). On top of that is the chip on a daughterboard that can be fitted to the socket. We provide a number (I think five) of chips mounted to daughterboards. In addition, we ship bare dies, unmounted. We may not continue to provide the Nucleo boards to the user, but we will continue to have a version of the development board that is pin-compatible with the Nucleo.