Help Some questions about particles

Here are some questions that I have difficulty understanding the use of particles.

1. やっと日本の生活に慣れました
Why is に used instead of を? Is 生活 not the object the speaker is trying to get used to?

2. 大阪で国際会議が開かれます
Why is が used instead of を? Isn't 国際会議 the object being opened? Or is this like をは becomes は (but replace は with が)

3. この小説はいろいろな国のことばに翻訳されています
Why is に used instead of を?

4. 先生の質問にすぐ答えるのが難しいです
Why is に used instead of を? Isn't the speaker trying to answer the question, so shouldn't the question be the direct object?

5. 宮崎さんに赤ちゃんが生まれたのを知っていますか
Why is it に instead of の?

6. パーティーに参加するかどうか、教えてください
Why is it に instead of を?

Thank you.

1)
生活 is the target, not the object. It's said that the verbs that take に have some kind of "directionality" such like ～に対して "towards". (Some verbs that take を also have directionality, for instance 北を向く, ゴールを目指す, though. )
The relation between verbs and particles in Japanese is similar to the one between verbs and prepositions in English. You need to remember whether the verb can take を or に(or other articles), i.e., transitive or intransitive after all. It would be hard to explain to non-native English learners why it should be "to enter a location" or "graduate from a school", and not "to enter to a location" or "graduate a school", right?

2)
Notice that 開かれる is passive.

3)
に indicates the result of the change here. (Have you ever seen ～に変わる "to change to~"?) いろいろな国のことば is not the object in the first place. There is no object in that sentence since 翻訳されています is passive also here.

4)
The same reason as #1.

5)
宮崎さん is a kind of location in this case just like 宮崎さんの家 "Miyazaki family". 宮崎さんの赤ちゃんが生まれた is grammatical, but this means "Miyazaki's baby was born", thus, it's directly talking about the baby, not Miyazaki, so it sounds a bit unnatural with 知っていますか. (In other words, 宮崎さんの赤ちゃんが生まれた is no problem as an objective description of an event.)

6)
The same reason as #1.

Thank you for your reply!

So for #2, because it's is passive, が is used instead of を?
But couldn't a sentence be like
私は誰かに自転車をとられました

For #5, is the reason for using に also because it's just used like that?

2)
国際会議 is the subject in that (passive) sentence. That's why it's indicated by が. が is not used instead of を.
Your example is "passive of adversity" (迷惑の受身) (and also "possessor's passive(持主受身)"). The direct passive sentence is （私の）自転車が誰かに盗られました. See the following post in detail.
Need a word or phrase translated? | Page 526 | Japan Forum

5)
The focus is put more on Miyazaki, not baby, in that sentence, so it's more common in conversations as a result.

Thank you very much!