if I remove all blocked contacts from my list, will that mean they can contact me again?

In case if you have not changed Apple ID they can still contact you through mails , even you unblock the contacts from mails preferences , once apple id is changed they will never knew your mailing address , suppose you had sent mails through web mail account , and that mail address was configured with IMAP account , and you block them still mail will strike at web mail server .