Answer to Question 1
The terminals are sealed through the metal case of the compressor. This seal is created during the manufacturing process. If a leak develops, the compressor must be replaced.
Answer to Question 2
The start winding of the hermetic compressor can be tested with an ohm meter by testing across terminals S-C. The run winding of the hermetic compressor can be tested with an ohm meter by testing across terminals R-C. The run winding should have a lower resistance than the start windings.