if I have 2 switches with only one link between them and no redundancy then add a new switch which has a lower BID than the other 2 switches over a single link do all my ports on all my switches transition into the listening then learning stage?
What would happen if the new switch has a higher BID?
Just the ports that are connecting the switches together would go into listening, learning then forwarding state. The switch with the lower Bridge ID will be come the root bridge. So if you connect a switch with a higher BID it will become a nonroot switch. STP will decide on this nonroot switch which port will forward or block traffic - this depends on your switch topology. There is much more on STP but I think this should answer your question.