Can I Link two routers together?

Yes. You need turn turn off DHCP and NAT in the second router. Connect each into the LAN ports, not the WAN ports. Then make the second router have the same ssid and password.

Yes. That way devices connected to the second router can talk to the first router to get to the Internet.

Most home routers are configurable for other use.

If you can and the device allows, you want to set it as Wireless Access Point (WAP) and hardwire it to your other router/WAP. Extenders/repeaters are terribad in general. They do nothing but repeat traffic from your original router/WAP. Bandwidth is chopped in half and you also have more wireless noise filling the air.

Extenders/repeaters have some use, but only in must use scenarios. Great, you extended the coverage of your wireless network, but oh crap, it's slow as hell.