Some questions about gse

first of all, thank you for your attention and I apologize in advance for some questions that may seem obvious. if there is a post maybe with a guide for GSE that would be great.
otherwise I hope someone can answer the following questions:
what changes between the loop block and the action block?

which of the various blocks is best to use to build a macro?

at the bottom some put the variables others actions on pressure or release or directly together, what would be the best way to fill in the bottom section of the variables?

does it make sense to insert multiple actions in a block?

does it make sense to use the /castsequence command?

Last but not least , why does the icon always remain with the question mark? and I don’t get the skill icons like in some builds I imported?

I’m Italian and I apologize in advance for my terrible English!