accepted full time offer and still apply for summer?

Hey Friends I have accepted a S&T return offer for full time position. However, coming from a non-finance background, I wish to experience a wider scope of finance. Thus, I am considering apply for another summer internship at IBD to experience. In London, Final year student can do internships. I can do this internship during the summer before full time starts. This can broaden my skill sets and let me determine what suits me the best. Do you think this is a risky move? How likely is my full time employer somehow find out that I am still applying for summer? What will their reactions being? Or is there a chance that during the background check for summer internship, they somehow contact my full time employer who gave me a return offer? Thanks for your opinions!