Huawei reuses the same interface for many of their routers, but chooses to hide some features. Some of these may not be supported by the hardware, but others may work fine.
The features are hidden using the HTML hidden attribute. To turn this attribute off for all elements on a page, open your browser's dev tools and type $('#*').show() into the console.
On my B315, this allows me to change the DNS server addresses sent via DHCP:
That's not something I can help with, unfortunately.
If you can find someone else that had success with your router model, and you're certain they're legit, you may be able to ask them for guidance. Otherwise, you'll just have to buy another router and make sure your SIM works in it.