Coding to compare 3 variables

This sounds a lot like a homework question. You can read the policy of this website regarding this here.
If you have a specific question, then plenty of people will be willing to help. As it stands your question is basically a call to solve your problem for you instead of helping you solve it for yourselves. Moreover, the way you've asked it is impossible to say anything since you didn't provide any data except for the names of the columns.
As a general feedback - try to look at descriptive statistics of different columns grouped by favorite restaurants. Also, take a look at the help for the t.test (type ?t.test in RStudio console for that) since you can't use default t-test since it assumes numeric data while you have ordinal responses.