Games labeled "Nintendo Switch 2 Edition" include technical and content upgrades:

The physical games of the "Nintendo Switch 2 Edition" do not include separate download codes. All content is completely on a single software card. This applies to games that were originally released for the Switch 1 and have been remastered for the Switch 2.
According to Nintendo, the packaging of these titles always contains the full, updated version. A subsequent download is not necessary for Nintendo-owned games. The upgrade is integrated on the storage medium. Users can resell or lend the game without restrictions.

All available Nintendo Switch 2 Edition titles can be found here

"Game Key Card" or "Software Key Cards" are different from regular software cards because they do not contain the full data of the game. The software key card instead acts as your "key" to download the full game to your console over the internet.
Once the game data has been downloaded, you can play the title by inserting the software key card into your console and launching the game.

You can find more information about "Game Key Cards" or "Software Key Cards" here
A selection of Nintendo Switch 2 games that are the "Game Key Card" can be found here

Yes! The Nintendo Switch 2 is backwards compatible with most digital and physical games from the first generation of Switch, as well as accessories such as Joy-Con (Gen 1) and the Pro Controller.

Please note:
Games that use special functions such as IR sensor or gyro control could work to a limited extent.

A full list of compatible & unsupported games can be found here

Free updates will be released for select Nintendo Switch 1 games, improving playability on Nintendo Switch 2. 
By connecting your Nintendo Switch 2 to the internet, you can download free updates that improve resolution or frame rate, or enable support for features like GameShare in select games. The content of the free updates depends on the game.

You can find a full list of all Switch 1 games that will receive a free update here

If you already own a Nintendo Switch console, you can easily move to Nintendo Switch 2! You can transfer your games, save data, and settings directly to your new console. You can also continue to use compatible Nintendo Switch games* and your Nintendo Switch controllers wirelessly on Nintendo Switch 2. Nintendo Switch Online members can continue to use the paid service on Nintendo Switch 2.

You can find more information here

Nintendo devices are backed by a 2-year manufacturer's warranty. Please note that we are not allowed to replace defective devices directly on Nintendo's instructions. Warranty claims and repairs must always be handled directly through Nintendo Service. For Nintendo service: Click here