Product development phase is the most important role in the product life cycle. As Dr. Simon mentioned, in the development phase you start to do:
Market Research, Design Control, Design Transfer, Approval, and IQ OQ & PQ. Because of the design control in the development phase, and design control is not only the right thing to do but also its very important to ensure safety and the product meet the user needs in the design control. Do a final check of your technical documentation, you may need to make updates.
Also in the development phase, make sure you have plans in place for “Post Market”.