the course and exam description provides a good bit of guidance on what you are and aren’t allowed to do as a teacher while administering the performance tasks. the explore guidelines are on page 72-73, here.
the list of things you absolutely can’t do as a teacher is pretty short, but one item is: suggest answers or provide feedback on answers to prompts (bottom of page 72).
providing students with a grade on their task submission would definitely be considered ‘feedback’, so this leaves you with limited options if you plan to use the actual explore task as a graded project in the first semester of the course. if the college board’s submission portal is available before your first semester ends, then you could have students submit their copy to be scored at the same time that they submit to you for end-of-term grading. but, as @cmeeks mentioned above, it can be tricky to give a summative assessment half way through the year. your students will continue to develop skills and knowledge that will be useful on the explore task between january and april, which means a task submission that’s locked down at the end of first semester might not be the best expression of what they know and what they can do. while it’s obviously your choice, and you know your students best, this is a tradeoff worth weighing carefully.
hope this helps clarify the feedback guidelines as defined by the college board in the course and exam description!