Ahmed, the uworld or amboss sources you wanted were already in my suggestion. The uworld source is the table in the extra section, that you all copied directly from uworld. The amboss source that they use is literally from the CDC, which was the article I linked in conjunction with the American Academy of Pediatrics, which both seem like pretty reliable sources to me...
https://www.cdc.gov/ncbddd/actearly/milestones/index.html
https://publications.aap.org/pediatrics/article/149/3/e2021052138/184748/Evidence-Informed-Milestones-for-Developmental?autologincheck=redirected
https://next.amboss.com/us/article/b40H3T?q=developmental+milestones#Za627b295a25831bcfa2e0ae76b0f4dc1
https://imgur.com/xZPRLZS
https://imgur.com/cSfRQnc