Вот образец заявления, по которому ты можешь заполнить свой бланк.

Вот often means something like here is, here’s, or look, here is.

In this sentence, it introduces the thing being shown to the listener:

Вот образец заявления = Here is a sample/model of an application statement

It is very common in spoken and written Russian when pointing something out or presenting something.

Because образец often takes the genitive case to show a sample/model of something.

So:

• образец = sample, model
• заявление = statement, application
• заявления = genitive singular of заявление

So образец заявления literally means a sample of an application/statement.

This is a very common pattern in Russian:

• чашка чая = a cup of tea
• центр города = the city center
• образец документа = a sample of a document

Заявление is a formal written statement, application, or request submitted to an institution or official.

Depending on context, it can mean things like:

• an application
• a written request
• a statement/declaration

In this sentence, образец заявления means a model example of that kind of formal written text.

Because по которому ты можешь заполнить свой бланк is a relative clause describing образец заявления.

Russian uses a comma before this type of clause, just as English often does before which or according to which, depending on the structure.

Main part:

• Вот образец заявления = Here is a sample of an application

Relative clause:

• по которому ты можешь заполнить свой бланк = by which / according to which you can fill out your form

So the comma marks the boundary between the noun and the clause that modifies it.

Которому is the dative singular form of который.

It is in the dative because it comes after the preposition по, which here requires the dative:

• по которому

The relative pronoun must match the noun it refers to:

• it refers to образец
• образец is masculine singular
• so the form is которому

A quick breakdown:

• который = which
• по которому = according to which / by which / following which

That’s right — here по is not physical. It has an idiomatic meaning closer to:

• according to
• following
• using as a model

So образец заявления, по которому ты можешь заполнить свой бланк means something like:

• a sample application according to which you can fill out your form
• a sample application you can use as a model to fill out your form

This use of по + dative is common when talking about doing something according to a pattern, example, instruction, rule, or template.

Compare:

• по плану = according to the plan
• по образцу = according to the model / following the sample
• по инструкции = according to the instructions

Because заполнить is perfective, and here the sentence refers to completing the action: filling out the form successfully.

• заполнить = to fill out, to complete filling out
• заполнять = to be filling out / to fill out in a general, repeated, or process-focused sense

After мочь, Russian often uses:

• perfective when the focus is on a single complete result
• imperfective when the focus is on process, repetition, or general ability

Here the meaning is: you can fill out your form using this sample, so the completed result makes заполнить natural.

Russian often uses свой when the possessor is the same as the subject.

Here the subject is ты, and the form belongs to you, so свой is preferred:

• ты можешь заполнить свой бланк

This is more natural than твой бланк in this sentence.

Compare:

• Я взял свою книгу = I took my book
• Ты открыл свою сумку = You opened your bag

Using твой is not always impossible, but свой is the normal reflexive possessive in this situation.

They are not the same thing.

• заявление = the actual written application/statement text
• бланк = a blank form or printed form to be filled in

So the idea is:

• here is a sample application
• you can use it to fill in your own form

In other words, the sample shows you what kind of information or wording to put into the blank form.

Yes. Ты is the informal singular you.

So this sentence is addressed to:

• one person
• in an informal or familiar way

If you wanted a formal version, you would usually say:

Вот образец заявления, по которому вы можете заполнить свой бланк.

Changes:

• ты можешь → вы можете

Everything else can stay the same.

Yes. The given sentence is understandable, but Russian speakers might also say things like:

• Вот образец заявления, по которому ты можешь заполнить бланк.
• Вот образец заявления, по образцу которого ты можешь заполнить свой бланк.
• Вот образец заявления, используя который ты можешь заполнить свой бланк.

The original sentence is grammatical, but по которому may feel slightly formal or official. In bureaucratic or instructional language, that is normal.

It breaks down like this:

• Вот = here is
• образец заявления = a sample of an application
• по которому = according to which / using which as a model
• ты можешь заполнить = you can fill out
• свой бланк = your form

So grammatically, the core is:

Вот [noun phrase], [relative clause].

More specifically:

• main clause: Вот образец заявления
• subordinate relative clause: по которому ты можешь заполнить свой бланк

That relative clause describes образец.