There’s a similar law where you must at least defend a trademark against misuse to keep hold of it. That was the reasoning behind this music video for Velcro:

https://youtu.be/rRi8LptvFZY

So, based on that, maybe they won’t lose it just by not using it. But if someone else tried to establish a Twitter product, they may lose the trademark if they don’t fight it.

I think there is, but AFAIK they can use it for something very minor and it still counts.