Beijing to UlanBataar (Mongolia) by bus and train

Hi. 1st of all thank you for your time helping many travellers from around the world.

I have a doubt. I will land from Vladivostok (Russia) to Beijing on the 4th August. My idea is to ask for a 144h visa, but I want to travel by bus and train to Mongolia. I see in one of your images (regions adopting 144 hours visa free policy) that inner mongolia is not painted, so I guess is not possible to travel in that area.

Basically, I need to know if I can apply for 144 hours visa even crossing Inner Mongolia on the way to Mongolia, or I have to apply for a normal toursit visa.

Thanks a lot.

Adrian