I wanted to start training her at 1.5 year old just like my mom did with me and my 6 siblings (Arab background). My American wife was resistant to the idea claiming it was too early and that she would go when she's ready. We ended up starting to introduce it at 2.5, but were too busy, lazy, not serious, etc. When she hit 3, we decided that was it and we took it seriously. Potty/toilet training for #1 was pretty easy and she was so good at it. However, #2 has been a nightmare and she hates not doing it the way she always did (in her diaper/pull up while standing up in a private place). She now goes #1 on her own (3 years and 4 months) and only calls us to help with cleaning. However, she cries or holds it until she no longer wants to go if we attempted to convince her to use the potty/toilet for #2. She will come tell us she needs to put on a pull up so she can go poopoo. She can go a whole night without peeing her pants. She can control her toilet needs when we are out. It's just the one old habit that she refuses to get out of.
We tried rewards and incentives, but she reached a point where she'd rather not get a huge surprise that she'd dying to have (e.g. telescope, piano) than to go #2 in the toilet.
We tried offering her paper on the floor so she can still stand or to go in the pull up while sitting down. No success. I wish I insisted to start at 1.5 or 2, but here we are. Any tips are highly appreciated.