Questions about image size

[ZZfive]

@Wangt-CN Thanks to your great work! I have a few questions about the generated image sizes:

1. Using the pretraing model currently provided, can only 256*256 images be generated?
2. Is it possible to generate larger size images without training?
3. If not, can larger size images be generated through training, such as 512*512?
4. Can the size of the generated images be variable, or should each size be trained separately?