1) CC1 and CC2 connections from microcontroller are properly connected to TCPP01-M12.
2) When TCPP01-M12 is separately powered up, input given to CC1 and CC2 appears on CC1_C & CC2_C
3) When input to CC1 and CC2 are given from the controller, the voltage is getting dropped in the input side of TCPP01-M12
I have attached the screenshots of the schematics for reference
All seems correct.
When TCPP01-M12 is powered and DB/ high, CC1 is connected to CC1c and CC2 is connected to CC2c. CC paths are closed. TCPP01-M12 embeds an OVP on CC1c and CC2c (>6V) to protect STM32 when short to Vbus line at cable removal.
At connection, a voltage drop may be observed when TCPP01-M12 close CC paths. Indeed, from connector point of view pull-down resistors of TCP01-M12 are replaced by pull-down resistors of STM32. That does not impact system.
If another behaviour is observed, can you share screenshots ?
External ESD protection (D601 and D602) on CC1 and CC2 PIN of STM32 (PB6 and PB4) can be removed because TCPP01-M12 also embeds ESD protections on CC1 and CC2 lines to protect STM32.
I recommend following the reference
design of X-NUCLEO-SNK1M1 that has been certified (USB-IF TID: 5205).
About USB Power Delivery on STM32, you can visit USB-PD Wiki pages.