The Pediatrician At The Clinic Explains Again, I'm Still Confused. Please Help.?

Again, I'm still confused. Please help.? - the pediatrician at the clinic explains

Just one question before I told my son of 9 months, a further 1 baby food step. Apparently it is already close to level 3, and I had no idea. We have a clinic for her and her pediatrician did not spend any time to say something. I feel like other mothers receive all approved manual and I'm completely out of the loop. I do not know when to change the food or anything. Now I hear you can give puffs and cornflakes, but my baby has only 2 teeth and can not understand how corn flakes are a choking hazard. Please someone explain it to me. Thank you.