1. If the project FW_CAR_SDK3_3 on your hands is read only status, you could select the folder and right click to select Properties. And make sure Read-only is not selected (the folder is read-only by default.) and set as Apply. The project could edit with PSoC Creator.
2. For CYPD3171 bootloader file, there are two ways can over come this:
One way: Copy CYPD3171 bootloader project from the SDK (C:\Program Files (x86)\Cypress\EZ-PD CCGx Power SDK\CCGx\Firmware\projects\CYPD3171-24LQXQ_pb\CYPD3171-24LQXQ_pb.cydsn\cc_sink_boot.cydsn) to your project directly and build the elf/hex files for your project. And update the Dependencies of Bootloadable. Refer below screen shot.
Other way: Select the CYPD3175 bootloader project you have, right click and Device select to CYPD3171-24LQXQ. And update the Dependencies of Bootloadable.