Racism: is a stronger type of prejudice used to justify the belief that one racial category is somehow superior or inferior to others; it is also a set of practices used by a racial majority to disadvantage a racial minority.
Discrimination: consists of actions against a group of people. Discrimination can be based on age, religion, health, and other indicators; race-based laws against discrimination strive to address this set of social problems.
Stereotypes: are oversimplified generalizations about groups of people. Stereotypes can be based on race, ethnicity, age, gender, sexual orientation—almost any characteristic.
Colorism:  is another kind of prejudice, in which someone believes one type of skin tone is superior or inferior to another within a racial group. 

Discrimination because they agent was choosing to not allow any other race except Caucasian live in the available house. 
2. Do you believe you have ever stereotyped someone (or treated them differently) by his or her accent or speech pattern? If so, how? 

Yes, I have, it is hard to know when someone has an accent, I often assume that they might not understand what I am saying. 
3. Is judging someone based on his or her accent or speech pattern different from judging that person based on his or her appearance? 
I think it comes from a similar mindset, however a person who discriminates on accent might not discriminate against skin color. Colorism focuses more on how a person appears, and some people could "pass" as white. 
4. Can you think of examples of this that you have seen or experienced?
Yes, a lot of times when I tell people I am half-Vietnamese, they automatically assume I come from a very traditional Asian household and assume I can speak Vietnamese. However my parents both grew up in the US and my family is American.