You won't be developing an app from scratch. We already have an app and it has some bug fixings and updates that supposed to be done here.
issues with ios chat app-
1. messages sent one are showing twice just one the screen of sender
2. Icons not showing animation when clicked (upload)
3. Expanded typing area shows weird behaviour after minimizing it
4. Remove all three icons from the bottom bar (basically remove the bottom bar)
5. Add Japanese language
6. Change sound for notification and call
7. The notification icon shows even after user is in chat page (went through the message) --> a confirmation is needed
8. During one to one call -> once minimized, can’t get the video to full screen.
9. Issue with video sharing from web to ios and vice versa
10. Screenshare not working from web to ios and vice versa
then in stage two ..
1. reduce loading time (allow offline storage of message like with other messaging app)
2. retouch the design for ipads (the design needs to be modified for larger screen) --> I will give you the design