Explanation
To add totals to a view using the Analytics pane:

Also, you can add totals from the Analytics tab in the Menu above:

Explanation
Measure names and values CANNOT be deleted in Tableau like other columns can. These are auto-generated.
Calculated Fields, and Number of records can both be deleted.

Explanation
**IMPORTANT QUESTION AND EXPLANATION, PLEASE READ**
3 ways to group data -
1) Marks
2) Labels
3) Dimensions shelf.
*IMPORTANT*
If we Group the data by selecting the marks, then they remain separate marks in the view and then have the same colour. Also, a new group is created in the Dimensions shelf. Example - Using the sample superstore dataset, first plot a bar chart showing sales for each sub-category:

Here, if we Select Phones, Chairs and Storage by selecting the MARKS (Bars), and then group them:

They remain seperate marks (BARS) but are grouped by the same colour.
Now, if we didn't do this, and rather grouped by selecting their Labels (Names):

Then they no longer remain separate Marks (bars) but are rather consolidated into a single Bar:

Finally, we can group directly from the Dimensions shelf as follows:

Now choose Phones, Chairs and Storage and Click Group:

You will now automatically have a new Dimension as follows:

Explanation
Tableau recognises a CSV file as a TEXT file, and therefore it is the correct option.
The following are the steps to import a CSV file:
1) From the data connection screen, click on Text:

2) Choose the appropriate file, and click Open:

3) Finally, Tableau imports the data as shown below:

Explanation
A histogram is a chart that displays the shape of a distribution. A histogram looks like a bar chart but groups values for a continuous measure into ranges, or bins.