How to redirect to reverse tunnel server with different port?

Setup:
Server A ( Hosted in private network, need VPN access )
Server B ( Public hosted )
Server C ( U can assume is my own macbook )

I use autossh to setup my reverse tunneling at server A
with this command autossh -f -T -M 20002 -o "ServerAliveInterval 10" -o "ServerAliveCountMax 2" -N -R 19999:localhost:22 user@server_b

Then in my Server B
I able to run ssh localhost -p 199999 to connect my server A.
Server B also enabled ssh port for 22 and 2022 at /etc/ssh/sshd_config

Problem statement:
How do I use command ssh user@server_b -p 2022 at Server C to redirect access the Server A tunnel from Server B?

Big picture
macbook -- ssh ( port 2022 ) --> server B -- redirect ssh ---> Server A

**must able to do scp task

1. To use a reverse tunnel automatically it is recommended to use autossh service.
2. I recommend to follow those steps:
3. Change keys between the servers you want to tunnel.
   • save your server A public_key on your server B /home/user/.ssh/authorized_keys file.
   • make the first connection manually with ssh user@serverB and see the connection is working fine.
   • do the same with server C - save your server B public_key on your server C /home/user/.ssh/authorized_keys file.
   • check the connection manually.
4. Now you have to redirect the ports you want with autossh - but first lets check that manually:
   • connect to your A server from your local pc with ssh user@serverA
   • on your server A shell - port forward the ssh connection from server A to server B with ssh -R <portX>:localhost:22 user@serverB
   • on your server B shell - port forward the serverA ssh tunnel with ssh -R <portY>:localhost:<portX> user@serverC.
   • now open another terminal on your local pc (without closing the existing terminal) and try to use the redirected tunnel with ssh user@serverC -p <portY> this should connect you to server A through servers C and B in the specific order.
5. Now after the tunnel seems to work fine we can automate the process by creating an autossh service (here is the one i am using):

[Unit]
Description=Keeps a tunnel to 'VPS' open
After=network-online.target

[Service]
User=root
ExecStart=/usr/bin/autossh -M portZ -i /root/.ssh/id_ed25519 -o "ExitOnForwardFaliure=yes" -o "ServerAliveInterval 30" -o "ServerAliveCountMax 3" -N -R portX:127.0.0.1:22 [email protected] 
Environment=AUTOSSH_GATETIME=0
Restart=always
RestartSec=3
StartLimitIntervalSec=0
StartLimitAction=reboot
StartLimitBurst=0
[Install]
WantedBy=multi-user.target

Now if you want to copy something into your computer with scp from server A just run the command on your local pc terminal:

• scp -P <portY> user@serverC:/path/path/filename localpcpath/path/.

Note: my answer assume that you have already created ssh keys and that your sshd_config file is configured well.