Could i get China visa at Hanoi without no-entry permit of Vietnam?

Hello, I'm Jeonghwan Kim from South Korea and I've been working in India. After 17th of June, I will travel Thailand, Laos and Vietnam without entry permit. And then I am considering going back to South Korean through PRC by land. So, I want to get a 90 days Chinese entry permit. But I saw many writings online that they said it became difficult since last year.

Can I get a single or multiple with the validity of 90days in Hanoi? and if it's possible, what would the cost be? and how long would it take? What should I prepare for it? Or it it's impossible, should I get L type of Vietnam?
Thanks!