Hierarchical Taxonomy Terms

Hello,
I am making a website in D6 for Classified Ad. I am using 2 vocab. 1st is City and 2nd is Category. Category vocab having parent and child term. My 2 questions are :
1) I want to show Category vocab's taxonomy term in hierarchical format with node count in 2column(column options can be editable). like :

Item for sale(20) Automobiles (60)
Art and Antiques(5) Auto Parts and Accessories(10)
Baby Stuff (5) Auto Services (30)
Collectibles (10) Used Cars (20)

Jobs (33) Real Estate For Rent (10)
Data Entry (2) Apartments (5)
Education (31) Houses (5)

Now when i click on parent term, all nodes will be displayed in teaser view whose associated with child terms and when I click on child term, nodes will be displayed whose are associated with it.

2) I created a page (content type) and both vocab is using in page. I have create a block view of city vocab and showing in left side bar.
Now my question is when I click on a particular city in left sidebar, then I want to show taxonomy terms like above format but node counting depended on city vocab. and when I click on parent term, all nodes will be displayed in teaser view whose associated with child terms (based on city) and when I click on child term, nodes will be displayed in teaser view whose are associated with it (based on city).

Above 1st question is for showing compile city vocab and 2nd question is for a particular city.

How can it possible? It can be done with views or another module should be used? Please elaborate in full details.

Thanks drupal.