Where is the whole bar rest placed?
In the middle of the bar
What can a semibreve rest be used for? Any exceptions?
A semibreve rest can be used to show a complete bar of rest in any time signature except 4/2 (which needs two of them)
What is a single thin barline used for?
A general divider into bars
What is a double thin barline used for?
Shows the end of a section or a key signature change