Adgangskoden åpner kodelåsen i åpningstiden.

In Norwegian, the definite article is usually attached to the end of the noun.

So:

• en adgangskode = an access code
• adgangskoden = the access code

The same pattern appears in:

• en kodelås → kodelåsen
• en åpningstid → åpningstiden

So Norwegian often expresses the with an ending like -en, instead of using a separate word.

Because Norwegian forms compounds very freely, much like German.

These are compound nouns:

• adgang + kode → adgangskode = access code
• kode + lås → kodelås = code lock / combination lock / keypad lock
• åpning + tid → åpningstid = opening time / opening hours

A useful rule is that the last part is the main word:

• adgangskode is a kind of kode
• kodelås is a kind of lås
• åpningstid is a kind of tid

English often writes similar ideas as two words, but Norwegian usually prefers one compound word.

The dictionary forms are:

• en adgangskode
• en kodelås
• en åpningstid

In the sentence, they appear in the definite singular form:

• adgangskoden
• kodelåsen
• åpningstiden

All three are common-gender nouns, so they take -en in the definite singular.

Because åpner is the present tense, while å åpne is the infinitive.

• å åpne = to open
• åpner = opens / is opening
• åpnet = opened

So in this sentence, Adgangskoden åpner kodelåsen means The access code opens the code lock.

Also, Norwegian verbs do not change form depending on the subject:

• jeg åpner
• du åpner
• han åpner
• adgangskoden åpner

That is much simpler than in English.

In context, it can be understood as opens in the sense of causes access or unlocks.

But there is a nuance:

• å åpne = to open
• å låse opp = to unlock

So if you want to be very explicit about the lock becoming unlocked, låser opp may be more precise.

Still, åpner is understandable here, especially if the idea is that entering the access code makes the lock open or release.

It means during opening hours or within the opening period.

This is an idiomatic Norwegian expression. You should not translate it too literally as in the opening time.

So:

• i åpningstiden = during opening hours
• utenom åpningstiden = outside opening hours

It refers to the time when a business, office, building, or service is officially open.

Because Norwegian often uses a singular noun where English prefers a plural expression.

So:

• åpningstiden can mean the whole period when something is open
• English often expresses that as opening hours

This is very normal in Norwegian. You may also see åpningstidene, especially when referring to a listed schedule of hours, but i åpningstiden is a common idiomatic way to say during opening hours.

The sentence has the normal main-clause order:

Subject + verb + object + time expression

• Adgangskoden = subject
• åpner = verb
• kodelåsen = object
• i åpningstiden = time expression

So the structure is:

Adgangskoden åpner kodelåsen i åpningstiden.

Norwegian main clauses follow the V2 rule, which means the finite verb is in the second position. If you move the time phrase to the front, the verb still stays second:

I åpningstiden åpner adgangskoden kodelåsen.

That sounds more marked, but it is grammatically correct.

Not exactly.

• adgangskode usually means an access code, often for entry to a building, gate, alarm system, or secure area
• passord usually means a password, especially for computers, websites, and online accounts

So in this sentence, adgangskode is the better word if the code gives physical access.

It is grammatical and understandable, but the most natural wording depends on the situation.

If you want to emphasize that the code works only during opening hours, a Norwegian might also say:

• Adgangskoden virker bare i åpningstiden.
  = The access code only works during opening hours.

If you want to emphasize unlocking, you might say:

• Adgangskoden låser opp kodelåsen i åpningstiden.
  = The access code unlocks the code lock during opening hours.

So your sentence is fine, but there are other versions that may sound more specific depending on what exactly you mean.