HI @Srinivas For your query, I do have the following points:
Character limit, there is no character limit being set in any field, it’s just the size of cards is fixed which will trunacte the data.
All the fields that are mentioned in docs.yellow.ai are mandatory.
No, optional fields.
No, you can’t change the card title, and there is no limit to the number of options that you can add to the card, but at a time we will show up to 5 options only, and if more than that we will enable load-more button which will again add up to 5 options in the card.