Moved from Canada to the US - Dual Status? File a Joint Return?

I wish I get your help! Here is my situation;

 

From Jan1, 2021 to October 17, 2021:

I was working in the US on H1B but living in Canada (Canada-US Commuter). 

 

From October 18, 2021 till December 31, 2021:

Still working in the US on H1B but moved to the US and still in the US through 2022. 

 

Throughout 2021 I have been with my wife who moved with me to the US. 

The household income is my US income only. 

 

Now, my questions are:

1- Can I apply for extension to satisfy the dual status requirements for both of myself and my wife?

2- Can we then (I and my wife) choose to be treated as residents for the entire 2021 year?? then we can file 1040 jointly. If so, how? 

3- If 2 can happen and we would be treated as a US residents, should I pay taxes back to Canada for 1/1-10/17 period which is now claimed to be a US residence? 

 

Thank you all for your help!!