To update the game on PC:
1. use the itch.io launcher.
2. Redownload the game and install over the original files.
3. If you're lucky and Steam isn't a health risk for you, and don't care about being DRM-free, use Steam.
To get pets:
1. Use Steam or the mobile version.
2. There is no 2. Pets aren't available on PC except on Steam. Devs, please fix this. It's literally not possible for me to use Steam, it is a health hazard and the company has knowingly refused to fix the problem for a whole year now. I would still like to be able to throw money at you for pets, but right now, you're not giving me an option to do so.