several question about 144 hour visa free transit

1. what is the onward ticket with a confirmed seat? is it same thing with onward ticket? Are there differences between onward ticket with a confirmed seat and onward ticket?

2. I want to buy e-ticket on web site of any airlines company for third country. Is it enough to get 144-Hour Free Transit when i arrive Shangai airport? For example, I want to fly from Singapore to Shanghai with A airlines and then i want to fly from Shanghai to Tokyo with B airlines.

3.Also here consider that check in for flight from Shangai to Tokyo will be made in Shanghai airport after arriving to Shanghai from Singapore. is it possible or can i get 144 hours free transit when i arrive Shanghai?