I was working on Lab - Switching and Routing, under Networking basis section of DevOps Pre-Requisite Course and I found that I can not access app01 through sudo ssh app01 command. It says I need to enter a password which I do not know. An it is not even mention in the instruction or in the question
As this infra is on cloud . Might be you find a .pem (key) in /home in each instance .
try to find in below location .
/home/ubuntu//home/user//root/
Command to find : find /. -name “*.pem”
if you got any .pem file then ssh to the app01
chmod 600 x.pem
ssh -i x.pem user@app01

