Explanation
Spark's DataFrames are equal to Python's or R's DataFrames.
No, they are not equal. They are only similar. A major difference between Spark and Python is that Spark's DataFrames are distributed, whereby Python's are not.

Explanation
Although the question suggests using a method called unique() here, that method does not actually exist in PySpark. In PySpark, it is called distinct(). But then, this method is not the right one to use here, since with distinct() we could filter out unique values in a specific column.
However, we want to return the entire rows here. So the trick is to use dropDuplicates with the subset keyword parameter. In the documentation for dropDuplicates, the examples show that subset should be used with a list. And this is exactly the key to solving this question: The productId column needs to be fed into the subset argument in a list, even though it is just a single column.
More info: pyspark.sql.DataFrame.dropDuplicates - PySpark 3.1.1 documentation Static notebook | Dynamic notebook: See test 1

Explanation
Correct code block:
spark.createDataFrame([("red",), ("blue",), ("green",)], ["color"])
The createDataFrame syntax is not exactly straightforward, but luckily the documentation (linked below) provides several examples on how to use it. It also shows an example very similar to the code block presented here which should help you answer this question correctly.
More info: pyspark.sql.SparkSession.createDataFrame - PySpark 3.1.2 documentation Static notebook | Dynamic notebook: See test 2

Explanation
DataFrame.repartition(6)
Correct. repartition() always triggers a full shuffle (different from coalesce()).
DataFrame.repartition(12)
No, this would just leave the DataFrame with 12 partitions and not 6.
DataFrame.coalesce(6)
coalesce does not perform a full shuffle of the data. Whenever you see "full shuffle", you know that you are not dealing with coalesce(). While coalesce() can perform a partial shuffle when required, it will try to minimize shuffle operations, so the amount of data that is sent between executors.
Here, 12 partitions can easily be repartitioned to be 6 partitions simply by stitching every two partitions into one.
DataFrame.coalesce(6, shuffle=True) and DataFrame.coalesce(6).shuffle() These statements are not valid Spark API syntax.
More info: Spark Repartition & Coalesce - Explained and Repartition vs Coalesce in Apache Spark - Rock the JVM Blog

Explanation
Stages with narrow dependencies can be grouped into one task.
Wrong, tasks with narrow dependencies can be grouped into one stage.
Tasks with wide dependencies can be grouped into one stage.
Wrong, since a wide transformation causes a shuffle which always marks the boundary of a stage. So, you cannot bundle multiple tasks that have wide dependencies into a stage.
Tasks are the second-smallest element in the execution hierarchy.
No, they are the smallest element in the execution hierarchy.
Within one task, the slots are the unit of work done for each partition of the data.
No, tasks are the unit of work done per partition. Slots help Spark parallelize work. An executor can have multiple slots which enable it to process multiple tasks in parallel.