144hours permit - onward, connecting flight INFO

Forgive me if this is a stupid question, but I need to clarify this.

When I arrive in China with the first flight and apply for my permit, do I need an "interline" ticket (same airline or an airline that cooperate with the first carrier) for my onward flight to a third country/region?

Can I buy the second ticket with a different airline as long as it departs from the same entry port and within the 144hours?

Thanks.
Dami