Correct spelling, explanation: beaten is an Old English verb, which looked similar to the contemporary word as it had the form bēatan. The origin of the word can be found in Germanic languages. In modern English beaten is the third form of to beat. The form beaten can also be an adjective.

Definition of beaten:
1. verb – past participle form of to beat, used when you defeated somebody in a game, etc., it can also refer to hitting somebody or someone as well as to producing a regular movement or sound, and to mixing ingredients while preparing dishes;
So far I have been beaten by him every time, but a day will come when finally I will be the winner.
He has beaten the drums a few times in his life, but it’s nothing serious for him.
My heart has beaten so irregularly recently that I need to make an appointment with my doctor.
Once you have beaten eggs with sugar, add the flour.
2. adjective – a flat ground or metal, such as gold or silver;
The path has been beaten here as so many people use this road as a shortcut.
He gave her a necklace of beaten silver.

Expressions with beaten:
1. beaten-up – old, damaged;
He drives a beaten-up car, which looks as if it was older than he is.
2. beaten down – usually refers to the sun which is really strong,
The sun has beaten down so strong today that it’s hard to do anything.
3. beaten yourself up – blame or criticize yourself, usually unfairly,
You shouldn’t have beaten yourself up for the accident – it was just bad luck.

Incorrect spelling, explanation: most English verbs are regular, which means that we add the -ed ending to a verb when we want to form the past simple or past participle form. If a verb is irregular, one needs to check its form. English users, especially learners often confuse regular verbs with irregular ones. Exactly that happens with the verb beaten, which is the irregular third form of the verb to beat, but many users create the form beated, which is incorrect.