1.) explain the difference between theory, universal law, and opinion. 2.) how do scientific theories differ from opinions?

1).A hypothesis is a statement that can be tested.   So the statement, "A watched pot never boils," is a valid scientific hypothesis because we can test it (and find that in this case it is NOT supported by the evidence).  

A theory is a general principle or body of principles  that has been developed to explain a wide variety of phenomena.  A scientific theory is NOT a wild guess.  It must be consistent with known experimental results and it must have predictive power.  As new knowledge is gained, theories are refined to better explain the data.

A law is a mathematical relationship that is consistently found to be true.  For example, one of the most famous laws in physics is Einstein's e=mc^2.
2).Scientific theory differs from a guess or opinion because a scientific theory is a system of ideas that explains many related observation and is supported by a large body of evidence acquired through scientific investigation while guesses and opinions may not reliably predict an outcome, have evidence to back up the reasoning, or they have not been tested.