Он молодец: всё сделал сам.

No. In modern Russian, молодец does not usually mean young man here.

In this sentence, Он молодец is a very common way to praise someone. It means something like:

• He did well
• He’s great
• Good for him
• He’s a star

So молодец is best learned here as a praise word, not as a literal age-related word.

No, молодец is a noun, but it is being used in a predicate after он.

So structurally, Russian is saying something like:

• He is a good one / a good fellow

But in natural English, you usually translate it more freely as praise.

A useful thing to remember:

• Он молодец = He did well / He’s great
• Она молодец = She did well / She’s great

So even though it is a noun, it works in a very common praise pattern.

Because in Russian, the verb to be is normally omitted in the present tense.

So:

• Он молодец literally looks like He good-fellow
• but it means He is great / He did well

This is normal Russian grammar.

Compare:

• Он студент = He is a student
• Она дома = She is at home
• Он молодец = He is great / Good for him

If you want past or future, Russian usually shows the verb:

• Он был молодец = He was great
• Он будет молодец is possible in some contexts, though less natural in everyday praise

Сделал is the past tense, masculine singular form of сделать.

It matches the subject он.

So:

• он сделал = he did
• она сделала = she did
• они сделали = they did

In your sentence:

• Он ... сделал = He ... did

The form tells you the subject is masculine singular.

This is a very important difference.

• всё = everything
• все = everyone / all (people or things in plural)

Here, всё сделал сам means he did everything himself.

So всё is the direct object of сделал.

Also note:

• ё is often written as е in everyday Russian writing
• so you may sometimes see все where the intended meaning is actually всё
• learners have to use context to tell which one is meant

But in this sentence, with the dots, it clearly means everything.

Сам here means:

• himself
• on his own
• without help

So всё сделал сам means that he personally did it all, and probably did not need help.

This word often adds emphasis:

• Я сам сделаю = I’ll do it myself
• Она сама написала = She wrote it herself
• Они сами пришли = They came on their own

In your sentence, сам stresses that he deserves praise because he did everything personally.

Because сам agrees with the subject он and is used for emphasis.

Here it is:

• masculine
• singular
• effectively tied to the subject

So:

• он ... сам
• она ... сама
• они ... сами

This is different from себя, which is the reflexive pronoun oneself and is used in different grammatical situations.

Compare:

• Он всё сделал сам = He did everything himself
• Он видит себя в зеркале = He sees himself in the mirror

So сам is the right word when you want to emphasize that the subject personally did something.

The colon shows that the second part explains or justifies the first part.

So the logic is:

• He’s great: he did everything himself

The second clause gives the reason for the praise.

Russian often uses a colon this way when the second part explains the first.

You could think of it as:

• He’s great, because he did everything himself

Because Russian often leaves out a repeated subject when it is already obvious from context.

So:

• Он молодец: всё сделал сам is natural
• Он молодец: он всё сделал сам is also possible, but sounds heavier

The subject of сделал is understood to be the same он from the first clause.

This kind of omission is very common in Russian when the meaning is clear.

Yes. Russian word order is flexible, and changing it changes the emphasis.

For example:

• Он молодец: всё сделал сам
  fairly natural; strong emphasis on сам at the end

• Он молодец: сам всё сделал
  puts earlier emphasis on сам

• Он сам всё сделал
  straightforward statement without the praise word молодец

In your sentence, placing сам at the end makes it sound especially emphatic: he did it himself.

Yes. Молодец is commonly used for women, men, and children.

For example:

• Она молодец = She’s great / She did well
• Ты молодец = You did well
• Вы молодцы = You all did well

But other words in the sentence will still agree normally:

• Она молодец: всё сделала сама

Notice the changes:

• сделал → сделала
• сам → сама

So молодец itself stays the same in Она молодец, but the verb and сам change to match the person.