Answer 1

Oh, there are different kinds of algorithm analysis.

In general, there seem to be two schools of thought in respect to the running time of algorithms: The first one is more on the theoretic side, it looks into asymptotic behavior of algorithms. In other words, which algorithm performs better given an infinitely large input.
The other one is more on the practical side, and is able to answer questions about the exact running time of an algorithm given an input of specific length.

Both have their merit. At Coursera, you can find algorithm courses by Tim Roughgarden about the first one, and by Robert Sedgewick about the second one.