If I cut my cell phone service off, can I still use it to call 911?

Yes. All cell phones can dial 911. And you can still get wireless internet.

Yes, as long as your battery is charged, you can still call 9-1-1. This is why some charities collect old mobile phones for redistribution to homeless and low-income persons. However, a mobile call may not be routed to the nearest response agency, and the agency won't have access to as much information about you.

Since landline phones are stationary, they can quickly be connected to their local emergency response agency, but a mobile caller could be anywhere, even if they possess active service. They may reach state police or highway patrol and have to identify their exact location in order to be routed to local response. In 2000, the FCC issued an order requiring wireless carriers to locate and transmit emergency callers, but follow-through on this order has been slow and hampered.

When a deactivated mobile caller eventually reaches the local operator, the operator will not have access to their former account information, since deactivated phone numbers are recycled. They will see that the phone is deactivated, and sometimes see the area code, but must request the caller's address. If disconnected, the operator will not be able to return the call.

Yes, you can still call 911 with your phone. And you can also still use the apps that are on the iPhone and use all non phone functions (games, apps, etc.), as long as you're connected to wifi.

Yes all phones can dial 911 even eithout service

Probably not, it will just become a toy with severely limited usage.

From what I understand the whole thing works on having a telephone line.

yes