A: Yes. When you assign a lead to a user from a company, or a form assigns one, that user gets an email whether they are active or inactive. An inactive user can't log in, so the lead won't be handled.
A form keeps assigning leads to the user it was set up with, even after that user is made inactive. In the form's assign settings, the user is then marked This user is deactivated. Leads assigned here will not be handled. Choose an active user or a role there instead. Leads given to a role only go to active users, and Assign to account manager if possible skips inactive account managers.
Read more about active and inactive users.