Can you still have spine deforming at 30, of you have sheaurmanns disease? or when does it stop deforming?

Scheuerman's disease: Yes. Adolescents typically develop a progressive cosmetic deformity, whereas adults with long-standing deformity typically develop pain and arthritis as an indication for treatment. Bracing has been demonstrated to be an effective treatment modality for the adolescent with a progressive deformity, while pain often responds to nonoperative care, including physical therapy and ibuprofen.

Depends: Most folks with schuermann's kyphosis are stable when they are adults. There could be some worsening after age 50-60 since the disks tend to get narrower with aging (in the mid back this might be resisted by the rib cage). If someone has osteoporosis, fractures could make the deformity worse (but this is not the scheurmann's worsening, it is the fractures).