Answer to Question 1
A manufactured part may measure either of the limits or any dimension in between the limits. This provides the manufacturer with some flexibility in creating the part.
Answer to Question 2
Step 1 Define the part's functions.
Step 2 List the functions by priority.
Step 3 Define the datum references frame.
Step 4 Identify the control sections from simplest to most complex.
Step 5 Calculate tolerances.