Good day, When I open the game in offline mode without internet, I can only play version 1.5, not version 1.6. What do I need to do or have to play version 1.6 without internet? I would greatly appreciate your response.

1.6 is a multiplayer patch, many things are not supported in single player mode e. g. AOC campaigns.

But if I wanted to play with a friend on a local network without an internet connection, how do I play patch 1.6 without internet?

I'm interested in knowing how to open patch 1.6 as if it were the executable file or something similar, also so I can play against the AI ​​when I don't have internet access

Again, you can't. If you want to set up a LAN, you can start both players in Single Player mode and set it up from there. But you need a little connection to launch the game from Voobly.