Upgrading postgres to 10 from 9.5 using pg_upgradecluster

I am testing the process of upgrading postgres to 10 from 9.5

I am following the steps as mentioned in this link
<https://gist.github.com/dmitrykustov/27c673ec4f7abd716912e4c830910019> -

dmanna(at)ubuntu:~$ pg_lsclusters
Ver Cluster Port Status Owner Data directory Log
file9.5 main 5432 online postgres /var/lib/postgresql/9.5/main
/var/log/postgresql/postgresql-9.5-main.log10 main 5433 online
postgres /var/lib/postgresql/10/main
/var/log/postgresql/postgresql-10-main.log

sudo pg_dropcluster 10 main --stop
sudo pg_upgradecluster 9.5 main -m upgrade
sudo pg_dropcluster 9.5 main

Can someone let me know the following

1. If there is a way I can check if the upgrade will be successful
before going for the actual upgrade?
2. If I am using the link option in the upgrade can I still use the sudo
pg_dropcluster 9.5 main?