1. What's the difference between 食べ, 食べるの, 食べたこと, 食べた物 and 食べたか?

Is the following correct:

食べが好きだ。
I love to eat.

食べるのが好きだ。
I love to eat.

昨日の食べたことが忘れた。
I forgot whether I ate yesterday.

昨日の食べた物が忘れた。
I forgot what I ate yesterday.

昨日の食べたか忘れた。
I forgot what I ate yesterday.

2. How do you use か as 'or'?

3. Am I correct to say that か is for statement, が is for questions, も means everybody or nobody?

私の弁当を誰か食べました。
Someone ate my lunch.

私の弁当を誰が食べましたか。
Who ate my lunch?

お前の弁当を誰も食べません。
Nobody ate your lunch.

I realize you're trying to understand the differences in the Japanese, but most of the Japanese sentences you give here are incorrect.

食べが好きだ。
(This is incorrect)

食べるのが好きだ。
I love to eat.

昨日の食べたことが忘れた。
(This is incorrect)

昨日の食べた物が忘れた。
(This is incorrect)

昨日の食べたか忘れた。
(This is incorrect)

2. How do you use か as 'or'?
You can use か between two nouns to mean 'or'.
E.g., クッキーかケーキ means "cookies or cake"
Unlike "or" in English, it can't be used with other parts of speech.

3. Am I correct to say that か is for statement, が is for questions, も means everybody or nobody?
I'm not sure what you mean.

私の弁当を誰か食べました。
Someone ate my lunch.
(This is fine, but usually the subject comes first in Japanese: 誰かが私の弁当を食べました)

私の弁当を誰が食べましたか。
Who ate my lunch?
(It seems like 私の弁当 should be a topic here, not an object: 私の弁当は誰が食べましたか？)

お前の弁当を誰も食べません。
Nobody will eat your lunch.

1. How about this:

食べ is the stem form of 食べる, right? I read somewhere that you can use them as noun. But how do you use them? Only for something like this? ご飯を食べに行く。

昨日は晩御飯を食べたことが忘れた。
I forgot whether I ate dinner yesterday.

昨日は晩御飯の食べた物が忘れた。
I forgot what I ate for dinner yesterday.

昨日は晩御飯を食べたか忘れた。
I forgot whether I ate dinner yesterday.

2. Can I use it like this?

りんごかみかんを買いますか。
Should I buy apples or mandarin oranges?

While we're at it, does this work too? I have seen it used with adjectives, but can you use verbs with it?

りんごとみかんと、どちらのほうが買いますか。
Between apple and mandarin oranges, which do you prefer to buy?

3.
私の弁当を誰か食べました。
誰かが私の弁当を食べました
Is my statement wrong or is there no need to place が if 誰 if it's in front of a verb?

お前の弁当を誰も食べませんでした。
Nobody ate your lunch. (Is this the correct tense? But why in past tense if nobody ate it?)

●食べ is the stem form of 食べる, right? I read somewhere that you can use them as noun. But how do you use them? Only for something like this? ご飯を食べに行く。
-How this works depends on the verb. In this case, the noun for food is 食べ物, and I've never heard 食べ as a stand in for that meaning. Usually there will be a separate dictionary defintion in a good dictionary for stems that can be used like regular nouns.

●昨日は晩御飯を食べたことが忘れた。
I forgot whether I ate dinner yesterday.
-It should be を忘れた
This sounds to me more like "I forgot that I ate dinner yesterday."
"Whether" would probably use 食べたかどうか

●昨日は晩御飯の食べた物が忘れた。
I forgot what I ate for dinner yesterday.
-This also should be を忘れた
Also, I'm not sure if this is a natural sounding Japanese sentence. I would phrase "I forgot what I ate for dinner yesterday" as "昨日の晩御飯は何を食べたか忘れた". But then, non-natives like myself are kind of bad at determining what sounds natural, and I'm not sure whether you can phrase this the way you did here (once you replace the が with を. As it stands now it's incorrect.).

●昨日は晩御飯を食べたか忘れた。
I forgot whether I ate dinner yesterday.
-This sounds fine.

●2. Can I use it like this?
りんごかみかんを買いますか。
Should I buy apples or mandarin oranges?
-This means "Will you buy apples or mikan?"

●While we're at it, does this work too? I have seen it used with adjectives, but can you use verbs with it?
りんごとみかんと、どちらのほうが買いますか。
Between apple and mandarin oranges, which do you prefer to buy?
-The りんごとみかんと park is correct, but it should be を買いますか, and I think the translation should be closer to, "Which will you buy, apples or mikan?"

●3.
私の弁当を誰か食べました。
誰かが私の弁当を食べました
Is my statement wrong or is there no need to place が if 誰 if it's in front of a verb?
-No, your statement is fine but is more characteristic of spoken language. が is often dropped in spoken language, regardless of whether the subject is directly before the verb or not.

●お前の弁当を誰も食べませんでした。
Nobody ate your lunch. (Is this the correct tense? But why in past tense if nobody ate it?)
-It's past tense in English (ate is the past tense of eat), and it works the same way in Japanese. Also, it's weird that you're using お前 with polite form.

私の弁当を誰か食べました。
私の弁当を誰かが食べました。
So, basically these two sentences are both the same but you'll find the second sentence on text?

I thought that the Japanese past tense works differently from English past tense. English's past tense is based on time while Japanese's past tense is based on whether something is 'finished'. Do you think this will work?

田中さんの弁当を誰も食べていません。
Nobody ate Tanaka-san's lunch.

By the way, thank you for your help. If I have any more questions in the future, do I post in this thread or create a new one?

Tzadeck Wrote:●While we're at it, does this work too? I have seen it used with adjectives, but can you use verbs with it?
りんごとみかんと、どちらのほうが買いますか。
Between apple and mandarin oranges, which do you prefer to buy?
-The りんごとみかんと park is correct, but it should be を買いますか, and I think the translation should be closer to, "Which will you buy, apples or mikan?"

Actually this one can mean "which one do you buy more" and thus "which one do you prefer." This can be made explicit by adding よく but it's not strictly necessary if the context makes it clear.

To the OP:

Quote:私の弁当を誰か食べました。
私の弁当を誰かが食べました。
So, basically these two sentences are both the same but you'll find the second sentence on text?

か is different. When you have a noun + か, you do not use が or を after it. With question words however, it can go either way. I think that either of these could be used in spoken or written.

Quote:食べ is the stem form of 食べる, right? I read somewhere that you can use them as noun.

As Tzadeck says, it differs depending on verb or construction. For certain constructions, like verb stem + に行く, you can use almost any verb there that makes sense. But if you're thinking about just using the stem as a general noun the way that 話（はなし） just means "talk", you just have to learn which ones are used and which ones aren't.

Quote:か is different. When you have a noun + か, you do not use が or を after it. With question words however, it can go either way. I think that either of these could be used in spoken or written.

Either way works? I see.

Quote:As Tzadeck says, it differs depending on verb or construction. For certain constructions, like verb stem + に行く, you can use almost any verb there that makes sense. But if you're thinking about just using the stem as a general noun the way that 話（はなし） just means "talk", you just have to learn which ones are used and which ones aren't.

So, the verb stem holds a different meaning from verb + no?