So is this app for learning python 3.x or 2x? Please answer

Answer 1

Clearly stated in the course :
This course covers Python 3.x, but it isn't hard to change from one version to another.

Answer 2

I suggest you download and rather use Python 3. Some examples and exercises in the tutorial may give hassles on 2 because 3 is not backwards compatible. The idea behind 3 not being fully compatible is to "neaten" things which are redundant/inconsistent/bad-practicey.
To get Python 3:
- Windows/Mac: Don't know, probably a download on the site.
- For Linux, most distros like Debian the default is 2.7 *but* python3 is usually also installed, so just setup the right path in you IDE ("which python3.x"), use the full path in your shebang at the top of the script, or call "python3 yourcode.py" from CLI. If you need to install it, "apt-get install python3" (or yum/pacman/whatever your distro uses for package management). It shouldn't change the default version as many apps/scripts are 2.7-dependant. So long as "python" still points to 2.7 you're clear.