dekakeru mae ni, mado ni kagi wo kaketa ka douka kakuninsimasu.

出かける前に means before going out.

It follows a very common pattern:

• verb dictionary form + 前に = before doing something

So:

• 出かける = to go out / leave home
• 前に = before

Put together:

• 出かける前に = before going out

A related pattern is:

• noun + の + 前に = before a noun
  Example: 食事の前に = before the meal

Because with 前に, Japanese normally uses the dictionary form of the verb:

• 出かける前に = before going out

The idea is that the action going out has not happened yet at that point.

This is different from English, where we do not really think about this as a grammar rule. In Japanese, it is a fixed pattern:

• Vる前に = before doing V

So 出かけた前に would not be natural here.

鍵をかける is a common expression meaning to lock something.

Literally, it is something like:

• 鍵 = lock / key
• かける = to put on / apply / hang

But as a set expression, 鍵をかける simply means:

• lock it
• lock the door/window/etc.

So in this sentence, 窓に鍵をかけた means locked the window.

A more formal word for to lock is 施錠する, but 鍵をかける is much more common in everyday speech.

In 窓に鍵をかける:

• 窓に marks the thing that the lock is being applied to
• 鍵を marks the thing being put on / engaged

So:

• 窓に = on the window / to the window
• 鍵をかける = put the lock on, lock it

This may feel a little different from English, where window would usually be the direct object of lock.

Japanese often expresses it more like:

• put a lock on the window

That is why に appears after 窓.

Because the speaker is checking whether the locking action already happened.

The sentence contains two time layers:

• 確認します = I check / will check
• 鍵をかけたかどうか = whether I locked it

So the checking is the main action, and the locking is an earlier action being checked.

This is very similar to English:

• I check whether I locked the window

Even though check is present/future, locked is past because it refers to the earlier action.

かどうか means whether or not.

So:

• 鍵をかけたかどうか = whether I locked it or not

This structure is used when you want to turn a whole clause into a yes/no content phrase.

Examples:

• 行くかどうか分からない = I do not know whether I will go
• 本当かどうか確認する = check whether it is true

Also, どうか here does not mean how.
In かどうか, it is part of a fixed grammar pattern meaning whether or not.

Yes, that is possible.

Both can be used:

• 鍵をかけたか確認します
• 鍵をかけたかどうか確認します

The difference is mostly nuance:

• か = whether
• かどうか = whether or not, more explicit

So かどうか spells out the two possibilities a bit more clearly. It is very common with verbs like:

• 確認する = check
• 知らない = not know
• 覚えていない = not remember

Good question. Both are possible:

• 鍵をかけたかどうか確認します
• 鍵をかけたかどうかを確認します

The version without を is very common and natural, especially in everyday Japanese.

The version with を is a little more explicit and can sound slightly more formal or careful in some contexts.

So in this sentence, omitting を is normal.

Japanese often leaves out subjects when they are clear from context.

In this sentence, the natural reading is:

• I check whether I locked the window before going out

But Japanese does not need to say 私 if that is already understood.

So the sentence can sound complete even without explicitly stating:

• who is going out
• who locked the window
• who is checking

Context supplies that information.

確認します means check, confirm, or make sure.

In this sentence, it has the nuance of verifying something carefully:

• I check whether I locked the window
• I make sure I locked the window

Because it is in -ます form, it is polite.

Also, 確認します is non-past, so depending on context it can mean:

• a habitual action: I check before going out
• an immediate/future action: I will check before going out

Both are possible unless context makes one clearer.

Both are natural, but they focus slightly differently.

• 窓に鍵をかける = lock the window
• 窓の鍵をかける = lock the window’s lock / fasten the window lock

In everyday English, both usually become lock the window.

A rough nuance difference:

• 窓に鍵をかける focuses a bit more on applying the lock to the window
• 窓の鍵をかける focuses a bit more on the lock that belongs to the window

In many situations, the difference is small, and both are used.