I can answer the 2nd Question now.. Use 9 decimal places for your calculator.. With 9 decimal places you can always find a round off for questions whose choice involves 2 , 3, 4 decimal places... And I doubt if answer choices will depend on your choice of decimal places to use.. 9 is really a safe bet.
I will try to answer the 1st question but please wait for further replies.. In case study type questions you will have more than one question from the same case.. And maybe questions which involve bonds, calculation of duration.. The very next question might be a modified duration calculation(which of course requires duration first) requirement to find out new price of the bond..
Examinees can answer this more accurately..
Adding to above,
regarding 1st question no The FRM exam is not structured like this totally.There might be some questions that could be structured like this but many are also isolated questions each checking a different concept as far as i know,may be a case with each question checking a different concept.
please see regarding 2nd question: https://www.bionicturtle.com/forum/threads/pre-exam-advice-and-tips.5875/ David recommends three decimal places usage for the calculator.