No. CFA Institute is aware that the HP 12C rounds up when computing the time required to accumulate a certain sum. We have taken that into consideration in the creation of questions and in the grading process.
The way ratios are calculated depends on the availability of data and how particular ratios are going to be used. There is no "one size fits all" solution, and such differences are part of the nature of financial analysis. Candidates should be familiar with the assigned curriculum and be prepared to perform calculations and interpretations based on that curriculum. If it is relevant, the exam questions will normally specify how the calculation is to be performed (e.g., "use beginning-of-year balance sheet data for your calculations"). Candidates must determine the most appropriate data to use in any calculations. The intended use of the ratio will help you to choose the appropriate data.
No. CFA Institute does not provide distribution tables with the exam. If a question requires information from a specific distribution table, that information will be provided with the question, but the tables themselves will not be provided. Similarly, time value of money tables (present value, future value, etc.) are neither needed nor provided. The two approved calculators are capable of performing any required present value and future value calculation.