A: Yes. Your tier is based on the number of unique contacts you send email campaigns to each month. A contact counts as soon as the email is sent, even if it bounces afterwards. Each contact counts once per month, however many emails they get.
Contacts whose email address has hard bounced are left out of later campaigns, so they do not count towards your tier again. The same applies to other emails Upsales does not send, for example to unsubscribed contacts or contacts with a missing or invalid email address.