Yes you can but it would be more cost effective to use 1 router (downstairs) and a network switch upstairs as each router will typically support up to 255 connected devices.
Yes, you can. Many routers have ethernet ports which you can use for LAN.
Yes, you can. It's "Bridge". PS: Not many routers support "Bridge". And it's a little bit tricky to set up.
Amazon provides useful consumer reviews for many different wireless routers. Another option would be to look at Consumer Reports and their ratings for different models.
Routers....
To stack routers means to physically stack routers. Some stack a couple of routers on top of each other if they plan to just use them as switches or similar.
Wireless N routers have better range and much better transfer speeds than G routers.
apple routers
Linksys routers are pretty much the same as all the other routers. Linksys routers got 8 PINS. You can find the PIN if you turn the router upside down.
Overlay Network is a logical network that runs on top of another network. No, it does not include routers. If peer X maintains a TCP connection with another peer Y, then we say there is an edge between X and Y. An edge in overlay is simply the tcp connection between a peer.
Modern networks used two devices for the data packets within the network will flow easily. The two devices are the routers and switches.
I bought a Netgear router and was good to go. I installed the package myself which at times was confusing but easy once you understand whats going on. You can pay to have someone set it up for you but if you have patience and good computer know how, then give it a try yourself! Signal is good from upstairs to downstairs also. Worth not paying a cable company to set up 2 networks. Along the lines of a cable company� many companies now allow you to rent wireless routers and have that be your internet service for your household. They set it up to which is nice for us that have no clue.
Some recommended books about Cisco routers are: Cisco Router Configuration, Cisco Routers For The Desperate, Cisco Routers for IP Router, Cisco CCNA Routing and Switching.