Even if you found a motherboard that fits your laptop and has better specs with a better processor (highly unlikely), it will be expensive. You are better off buying a better laptop and transferring your stuff over.
No you can't. Processor upgrades are only possible on desktop computers.
That's not true at all. As long as the processor isn't soldered (some are, some aren't) then all it takes is some research to find what will work on the motherboard.
see if your cpu is in a socket or soldered to the motherboard as most likely is in a socket as all the scrapped laptops I have for parts, the cpu's are in sockets.