gefordert
required
Needed or demanded in order to fulfill a particular condition or complete a task.
Die geforderten Unterlagen müssen bis spätestens Freitag eingereicht werden.
The required documents must be submitted by Friday at the latest.

required / challenged
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required
Needed or demanded in order to fulfill a particular condition or complete a task.
Die geforderten Unterlagen müssen bis spätestens Freitag eingereicht werden.
The required documents must be submitted by Friday at the latest.

The word 'gefordert' (required/challenged) is the past participle of the verb 'fordern' (to demand, to require). It is used like an adjective to express that something is required or that someone is challenged.
Für diesen Job ist ein abgeschlossenes Studium gefordert.
A completed degree is required for this job.
When 'gefordert' (required/challenged) appears before a noun, it usually means 'needed' or 'required'. When it appears after a verb like 'sein' (to be) or 'sich fühlen' (to feel), it usually describes the state of being strongly taxed mentally or physically.
Die geforderte Summe war einfach zu hoch.
The required amount was simply too high.
In the meaning 'needed', 'gefordert' (required) often appears with nouns that describe requirements. Typical examples are: die geforderten Qualifikationen (the required qualifications), der geforderte Mindestlohn (the demanded minimum wage), die geforderte Leistung (the required performance).
Erfüllen Sie die geforderten Qualifikationen für diese Stelle?
Do you meet the required qualifications for this position?
To express that someone is challenged, 'gefordert' (challenged) is often combined with verbs like 'sein' (to be), 'sich fühlen' (to feel), or 'wirken' (to seem). Adverbs such as 'sehr' (very), 'voll' (fully), or 'kaum' (hardly) strengthen or weaken the statement.
In meinem neuen Job bin ich endlich wieder richtig gefordert.
In my new job, I finally feel properly challenged again.
necessary
'nötig' and 'gefordert' can both express that something is needed for a task or condition. 'nötig' is more general and more neutral. It is used for many everyday situations: money, time, documents, or help can be 'nötig'. 'gefordert' sounds more like a rule, task, or expectation. It fits well when someone requires certain skills, performance, or documents. In short: 'nötig' describes what you need; 'gefordert' more often describes what is required.

Bei der Bewerbung sind gute Deutschkenntnisse gefordert.
Good German skills are required for the application.
Für die Prüfung ist viel Übung nötig.
A lot of practice is necessary for the exam.