Understanding あんなの見に行ったの

Question

From the first episode of Death Note:

マジで？ あんなの見に行ったの？

Questions:

1. I know that "あんな" (labeled as a "pre-noun adjective" in my dictionary) means "that sort of thing". Grammatically, is this word just あん + な (where あん is a な-adjective, and the な is just being appended to it to allow it to modify a noun)?

2. Is the の after あんな "nominalizing" あんな?

3. Is 見に行った seen as a single word, or is it (見 + に) + 行った? If the latter, does adding に to verbs transform to the infinitive form? So for example does 見に mean "to see", in this context (so that the whole sentence means "You came to see that sort of thing"?

Answer 1

School-grammatically and according to デジタル大辞泉, あんな is na-adjective (形容動詞). From the entry (bold added):

あんな has two pre-noun forms あんな and あんなな. Usually あんな is used, but before ので/のに, あんなな is used. E.g., 事態があんななので、どうすることもできない.

So rather than あん+な, it is あんなな with the last な dropped.

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The の here is 準体助詞 （a related question）:

２ （活用語に付いて）その語を名詞と同じ資格にすることを表す。「読む―が速い」「彼を行かせる―はまずい」「こんな―が欲しい」→

So yes, の is nominalizing あんな.

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Generally a particle connects to specific forms of verbs (possibly comparable to prepositions connecting to specific cases of nouns in some European languages).

The relevant definition of に is:

［格助］名詞、名詞に準じる語、動詞の連用形・連体形などに付く ５ 動作・作用の目的を表す。「見舞い―行く」「迎え―行く」

For the particular case, 見 is 連用形, not infinitive form (I assume it to mean stem).

Practically "Verb (連用形) + に行く" means "go to/and V". From foreigners' grammar perspective, 連用形 covers both te-form and masu-form. And the form that comes before に行く is masu-form. Hopefully someone corrects me if I'm wrong.