I'm not sure what you mean, what are you expecting Google Optimize to receive? How did you set it up?
This is currently not the case. Webflow's default form submission is via AJAX and do not change the URL in any way. Do you mean that this is required for Google Optimize, but has not been done yet?
This is not the case. The confirmation/success message ("Thank you! ...") did show up when I submitted the form. Did you mean something else when you say "Confirmation message"?
As long as you have set a notification email address in the Site Settings, and the form's default action has not been modified (to submit to Webflow), you should be receiving the form submission via email from Webflow. Did you mean something else when you say "notifications are not sent"? What notification are you expecting from where?
Please describe the problem in detail.