Your problem here is that you are on app01, and not on the jump host. The jump host is configured to ssh into all of the other hosts w/o a password, because the jump host’s key is deployed on the app hosts. But the app hosts are not similarly configured; their keys are not deployed on the other hosts. So to ssh from app01 and other app hosts, you need to know a password. Which you don’t know in this lab.
The solution when you need to ssh into app02 or another host is to go back to the jump host, and do it from there.
Sir, could you please explain how to return to the jump host and perform the tasks from there?
try exit or Ctrl + d
look at the text in green colour thor@jumphost. That implies you were on jumphost server.
From the jumphost you will have to shh to each app and perform necessary actions.
On jumphost: ssh app01
On app01: do whatever you are supposed to do
On app01: exit #to come back to jumphost
Similarly do it for rest of the apps.
There was a lab where the password was given for the app01 server in the question
I tried using that password for app01 servers on other labs, but that didn’t work 
The key here is understanding why you don’t have to use a password in some contexts. In this lab, all the keys are installed on thor@jumphost. IF YOU ARE NOT ON thor@jumphost, THE KEYS ARE NOT INSTALLED. So you need to;
- look at the prompt to see what host you are in.
- if you are not seeing a prompt of thor@jumphost, please type “exit” to go from that host back to thor@jumphost.
- If you do see thor@jumphost, you’re in the right place, and if you type “exit” in this context, you will terminate your lab. DON’T DO THAT.
Thank you, sir, It works