When all outcomes are equally likely?

Answer 1

... then all outcomes are equally likely. Nothing more, nothing less. You can always re-define the outcomes so that they are not all equally likely.

For example, on a single roll of a fair die, the numbers 1 to 6 are equally likely. But redefine the events so that

Event A = Prime number

Event B = composite number

Event C = neither prime nor composite number

then P(A) = 1/2, P(B) = 1/3 and P(C) = 1/6 : events with unequal likelihood.