Questions on Scrum Guide

Hi Scrum Masters,

I need some help to clarify some topics in the Scrum Guide

Sprint Planning
- Why the Sprint Goal is defined after DT finishes the forecast for PBI? Would it be better if the Sprint Goal is defined prior to selecting the PBI to be delivered in the Sprint?
- On page 9 of the guide, it states that "Work planned for the first days of the Sprint by the DT is decomposed by the end of this meeting, often to units of one day or less"? Does this mean that beyond the first days, the work becomes longer or harder in more than a day? Does it mean that easy PBI being worked on first before the harder ones?
- What is the difference between the Sprint Goal and objective set by PO during Topic One?

Daily Scrum
- Is it mandatory for SM to attend the Daily Scrum? Can he/she attends only if there are impediments that will be highlighted by DT?
- Does DT need to use yesterday Sprint Backlog as input to the meeting?
- Does the output of the meeting require updating the Sprint Backlog, to mark those completed items and log the identified impediments?

Sprint Review
- In this event, you will need both PB and SB isn't? The expected output will be a revised PB to indicate the probable PBI for the next sprint?
- Is there a rule when a Sprint Review must take place in relation to production release?

Sprint Retrospective
- What are the responsibilities of the PO in this event?
- Where do you "create a plan for improvements to be enacted during the next Sprint"? Is this broken down as PBI and added to the PB?

Scrum Artifacts
- At which event does the Product Backlog is created?
- In the Sprint Backlog, does DT need to indicate the estimate of each task for all selected PBIs?
- Can I say that the Increment is not a document but rather a product version that can be released to production?