Maybe if prolonged. If there's a major change in posture, in the long run there's also a risk for strain and pain. Prevention is best. Step one is to stop using the device so often and/or try a different one like a tablet. Next one could also consider yoga or physical/occupational therapy if primary care doctor approves. If there's a problem after stopping using the phone or tablet, then a physiatrist could be seen.
"text neck" Chronic use of any device that requires looking down for extended periods might cause problems with the cervical spine in the neck and upper shoulders. Taking breaks often and changing positions might help prevent long-term problems.
No. Unless you are sitting in a bent position or any other position that strains your back while you are texting, it is unlikely that it will mess up your spine.