Questions about visiting Boston during Christmas through New Years

Hello! Me, my wife and our friend will be visiting Boston during the holidays. We will be there for a week. We are planning to either stay in Framingham or downtown Boston. I have some questions for our visit.

1.) What is the weather like up there late December? Does it snow a lot?

2.) Should we rent a car? I figured we wouldn't need to if we stayed in Downtown, but for transportation to Framingham, will a car be necessary? Is transportation between Framingham and Boston reliable?

3.) If we did rent a car, should we get a car that would do well in wintery conditions? The cheapest rental is a convertible lol.

4.) We are planning on visiting Portland, ME. Is Amtrak the best way to travel?

Thank you in advance!