How to upgrade extension without loosing data?

Hi All,

How do i upgrade my extension v1(NAVX) without loosing data?

i have reffered below links 

https://community.dynamics.com/nav/f/34/t/244086

https://docs.microsoft.com/en-us/dynamics-nav/extensions-upgrade-howto

and also i have below quesations.

1. NAVAPP.GETARCHIVERECREF how this function works and what is NAVAPP(installed app or Archived data app?)

2.NAVAPP.RESTOREARCHIVEDATA here also NAVAPP which one can take?

is this possible to debug upgrade code unit then how?

any other way to upgrade data for extension 1 not through AL?

Please suggest me to resolve?

Thank you

Ramesh