My advanced computer Vision Assigment (Or : how to make an angry giraffe to disappear)

The university task of my CV course asked me & my friend (let's call him UV) to take the basic knowledge that we acquire into something practice and cool one. 

We had to take a movie from the internet (that's take from one fixed point) 

and fulfill the 3 missions bellow:

1) remove any object from the movie.

2) insert a fixed object into the movie.

3) Tracking a motion object inside the movie.

Surprisingly or not, all those 3 tasks related to a one feature that known to all:

Panorama feature. (the feature that take a wide-angle shot by attaching several pictures)

BTW- this is why the requirement to take the movie from one single fixed-point.

-So what is the technique behind the scene?

1)

2)

3)

The code:

The videos :

1)Remove

original video: 

remove giraffe:

2)Insert

original video:

inserted object:

 

3)Tracking

TDB