I can't answer your first question, but I have some reference to the age. My friend started her girl when she was about 12 months. Not fully, but every time she went to the bathroom, she'd put her girl on her little potty (she was walking pretty well at this age too). She's now 14 months and she'll go during the day on the potty (but obviously still wears diapers). On the other hand, her step mother has a 5 year old that has been out of diapers for only a year. They had to potty train her so she wasn't going to kindergarten in diapers. IMO, 3 is pushing the age to when they need diapers, so I think they should be trained by the time they are 2.5. Kiara sounds likes the perfect time to start full on. Good Luck!

Thank you for response

She is doing good during the day, but at night time we still put diapers on her and if we go out. At first, at home we would just let her run around with just a shirt on and she did really good going to the potty now we put undies on her and she has some accidents with then on, but is getting better ever day. She picks things up fast. I think she will be trained by 2.5.