How can I determine what technologies are installed on a stack?

These details can be provided by the creator of a content.

Are there disk size limits to each sandbox?

Yes, depending on what the creator of the content set, there will be either a 256MB, 512MB, or 1GB limit on the disk size.

Are there network limits for each sandbox?

Yes, depending on what the creator of the content set, there will be either a 25Mbit, 50Mbit, or 100Mbit limit on downloads, as well as a 25Mbit limit on uploads.

Are there other limits for each sandbox?

Yes, also based on what the creator of the content set, there is a 256MB, 512MB, or 1GB limit on memory usage, as well as flexible CPU limits.