Пусть плакат и простой, но благодаря наклейкам и аккуратному эскизу он выглядит интереснее.

Not exactly. In this sentence, пусть is not giving permission or making a command.

Here it works as a concessive particle, meaning something like:

• granted
• even if
• although
• it may be true that

So Пусть плакат и простой, но... means roughly:

The poster may be simple, but...

or

Although the poster is simple, ...

This is a common Russian pattern for admitting one point and then contrasting it with another.

That и is part of the concessive pattern. It does not simply mean and here.

In structures like:

• пусть ... и ..., но ...
• хотя ... и ..., но ...

the и adds emphasis, something like:

• even if it is indeed...
• yes, it is ..., but...

So Пусть плакат и простой, но... is more natural and idiomatic than reading и literally as and.

Both are possible in Russian, but they are slightly different in style and feel.

• простой = full adjective form
• прост = short adjective form

Here, Плакат простой is the more neutral, everyday way to say The poster is simple.

Плакат прост is also grammatical, but it sounds more literary, concise, or formal.

So in this sentence, простой is the most natural choice.

Because it agrees with плакат, which is the subject.

In the present tense, Russian usually omits the verb to be, so:

• Плакат простой literally looks like Poster simple
• but it means The poster is simple

Since плакат is masculine singular nominative, the adjective is also masculine singular nominative:

• плакат → masculine singular nominative
• простой → masculine singular nominative

Because благодаря governs the dative case.

So:

• наклейки → наклейкам
• эскиз → эскизу

This is just a rule of the preposition.

Благодаря usually means thanks to or due to, often with a positive or at least favorable nuance. In this sentence, it means that the poster looks more interesting because of / thanks to the stickers and the neat sketch.

They are both in the dative, but one is plural and one is singular.

• наклейкам = dative plural of наклейки
• эскизу = dative singular of эскиз
• аккуратному agrees with эскизу, so it is also dative singular masculine

So the difference is caused by number:

• multiple stickers → наклейкам
• one neat sketch → аккуратному эскизу

Because аккуратный has to agree with эскизу, and эскизу is:

• masculine
• singular
• dative

So the adjective must also be masculine singular dative:

• аккуратный → dictionary form
• аккуратному → masculine/neuter singular dative

This is standard adjective agreement.

Because интереснее is the comparative form: more interesting.

• интересно = interestingly / interesting in some contexts
• интереснее = more interesting

So:

• выглядит интересно = looks interesting
• выглядит интереснее = looks more interesting

The comparative makes sense because the speaker is contrasting the poster’s simplicity with the extra visual appeal created by the stickers and sketch.

Russian often leaves the second part of a comparison unstated if it is obvious from context.

So он выглядит интереснее can mean:

• it looks more interesting
• it looks more interesting than you would expect
• it looks more interesting than before / than a simple poster normally would

You only need чем when you explicitly name the thing being compared:

• Он выглядит интереснее, чем раньше = It looks more interesting than before
• Он выглядит интереснее, чем другие плакаты = It looks more interesting than the other posters

Yes, Russian could omit он here, and the meaning would still be clear in many contexts.

But including он does a few useful things:

• it clearly restates the subject after the long introductory phrase
• it makes the sentence flow more naturally
• it strengthens the contrast: yes, it is simple, but it looks more interesting

So он is not strictly required, but it is very natural.

Yes. Хотя плакат и простой, но благодаря... would be very close in meaning.

The difference is mostly in nuance:

• хотя = straightforward although
• пусть = granted / even if / be that as it may

So пусть can sound a bit more like the speaker is conceding a point before making the main argument.

Both are possible, but пусть gives the sentence a slightly more rhetorical feel.

Because но introduces the contrasting main clause.

The sentence has this basic structure:

• concessive part: Пусть плакат и простой
• main contrasting part: но благодаря наклейкам и аккуратному эскизу он выглядит интереснее

Russian normally separates these parts with a comma, especially before но.

So the punctuation reflects the meaning:

Even though the poster is simple, it looks more interesting thanks to the stickers and the neat sketch.