When you unblock someone, they will be able to email you again, and future messages from them will no longer go straight to your Spam folder. However, note that that were already sent to spam; you will only receive new emails moving forward.
No. Google does not send a notification to the person when you block or unblock them. how to unblock people in gmail
Block an email address in Gmail - iPhone & iPad - Google Help When you unblock someone, they will be able