No. Universal Design for Learning (UDL) is a framework for instruction and learning, therefore it can and should be your guide for all students. Applying UDL principles allows practitioners to effectively break down barriers to provide instruction to all learners, regardless of ability. While it might be essential for students with IEPs or 504 Plans, the framework is beneficial in meeting the needs of every learner.
No. UDL is an overarching approach aimed at eliminating barriers in the classroom, instruction, and learning environment. Differentiation is a strategy aimed at individual student needs. UDL is a proactive approach, meaning it occurs in the lesson design.
No. "Learning styles" are stagnant while learner variability is flexible based on multiple factors including content and context. For example, a student who typically identifies themselves as a "visual learner", may find that during a fractions lesson they need the tactile representation from the use of concrete manipulatives prior to the visual representation of the same concept in order to be successful.