changing web content but still google analytics tracks the page

Here is a website a let say a.com with a.com/xxx or /yyy
I am now the webmaster and i don't know the initial setup of the web.
It used google analytics to track webpage info.
And it is assumed the web is attached with javascript tracking code.

The webpage reforms and it is now with no tracking code.
However, there is still tracking info until today. Some of the hierarchy of the website remains.

Q1. Why google can still track the website?
I guess that's because of the unchanged hierarchy.

Q2. Can i see individual user pathway / history? Now i can see the summary of each day / hour with total. What I want is user a /xxx -> /yyy / a.com -> /yyy

Q3. I still want to use google analytics service. How can I make sure it works fine?
Status now: receiving data, which I barely trust. Answer of Q2 leads to Q3.
If I can see there are some users viewing the new page e.g. a.com/zzz, then i know new webpage is being tracked.

Newbie to web.
Comment appreciated.