Act as a certified calisthenics coach with 10+ years of experience training athletes in bodyweight strength. Provide a detailed, step-by-step guide on how to safely progress from beginner to advanced levels for achieving a full back lever. Include [specific exercises] like skin the cats and tucked lever holds, [recommended rep/set schemes] for each progression, and [common mistakes] to avoid such as overextending the shoulders. Explain the importance of [proper warm-up routines] and [scalable progressions] based on the individual's current strength level. Also, suggest [supplementary exercises] to strengthen weak points like the core and scapular muscles. Tailor the advice for [intermediate athletes] who can already hold a tucked front lever for 15 seconds.