How to add parameters in QLIKVIEW??

[#1]

I had working on SSRS for quite sometime. Now our company is planning to switch to QlikView for its better data visualization capability.

I have few questions as a newbie.

1. Is there any mechanism to add parameters in Qlikview?

2. What i want to implement is below

Four parameters which will have Custom values

i.g

     Group1 :  Continent , Country , State , City

     Group2 :  Select ,Continent , Country , State , City

     Group3 :  Select ,Continent , Country , State , City

     Group4 :  Select ,Continent , Country , State , City

Dimensions  : Continent , country ,State , City

Measure : SUM(Population)

Scenarios :

1. When User selects Continent,Select,Select,Select in four parameters then output must show Continent & Population

2. When User selects Continent,Country,Select,Select in four parameters then output must show Continent,Country & Population

3. When User selects Continent,Country,State,Select in four parameters then output must show Continent,Country,State & Population

4. When User selects Continent,Country,State,City in four parameters then output must show Continent,Country,State,City & Population

How could i do this in QlikView?

3. Is there ability to set expression on subtotals ? Could i use parameter values in subtotal expression ?

Thanks