It can be written as a data block separate from the HTML, making it useful for maintenance. However, changes in price, name, date, etc. in the text must be managed so that they are reflected in the data.
Multiple types can be represented together, but they only contain what the actual page describes. You must not add reviews, authors, or content that does not exist.
After checking the JSON syntax and Schema.org semantics, the types supported by Google are checked separately for search function conditions. Rich Results Test does not support all Schema.org types.