what if someday when bitcoin has become the main payment instruments in the world. and how when the Internet network paralyzed. it means that we all can not perform various financial transactions? , is there any solution ?
I don't know what you understand from the word Internet but it is not a commodity or something rather it refers to inter-connectivity of computers around the world. Thousands and thousands of servers and gadgets are dedicated for uptime of this connectivity. So I can't think such situation ever occur considering Bitcoin will be main payment option. This will induce more concern and safety towards internet!!
Yes. Also consider that where there's a will, there's a way. Even if big areas of the internet were to go down, it would seem to me that this would not last long as there are so many tech-savvy people that would manage to get themselves connected and would be likely to help their friends and buddies to get connected who themselves, would be helping their friends and buddies and so on and so on.