Hi. These terms are very similar in meaning. They are all actions resulting in an attack.
If we only use the context of a fight between people, you could explain the differences like so:
To strike someone = to hit someone. You can always exchange the word strike and hit in a sentence, and it will not change the meaning of the sentence.
Perhaps to "strike" is a stronger word. Aslo, perhaps it is more literary, it could be chosen over to "hit" when telling a story.
To beat someone = to give someone a beating. This is an act of repeated violence against someone that results in injury.
In the context of a competition, team A beat team B, it means team A won.
J.