If you backed up your game folder yes you can. Most games on Steam have no DRM, so just copying the folder is enough to play it on another computer. Then there are badly implemented games which you would need to replace the steam library with an open implementation (which doesn’t involve cracking the game). And finally there are games with DRM which are not available on GOG so they’re irrelevant to the discussion.
No it’s not. If Steam goes down you cannot keep playing your games without using a crack to get around the DRM.
If you backed up your game folder yes you can. Most games on Steam have no DRM, so just copying the folder is enough to play it on another computer. Then there are badly implemented games which you would need to replace the steam library with an open implementation (which doesn’t involve cracking the game). And finally there are games with DRM which are not available on GOG so they’re irrelevant to the discussion.