this is the kind of stuff you should be trying out yourself to learn, once you get into it its great fun!
first paragraph: variable assigning and if statement
second paragraph: read up on the prompt method, store it in a variable and use an if statement to check
third paragraph: use a prompt for each and store them in a variable each, use alert() to print the information out using concatenation ("string" + var)
fourth paragraph: read up on for loops, a prompt and if statement at the beginning should solve this.
have a go at it and post what you can, im sure everyone will try and help