What kind of posts do you mean? And what are "code blocks"?
If those are just pieces of code, then you can easily paste them at least within forum posts without problems.

Hey Sis, long time no see.
I want to use my site to teach programming and coding. I don't the HTML/css/javascript etc to be translated into texts or images/boxes. I want the code the appear as it was written .

example
var number = prompt(Please enter a number to calculate its square root");
var answer = Math.sqrt(number);
document.write("The Square Root Of " + number + " is " + answer);

and if possible the codes should be colored depending on the language.

Sounds like this should be done as a separate plugin.

I recommend integrating one of the existing e-learning systems.