You are "seeing" the wrong 「どれ」 here, which is the 「どれ」("which one") from こそあど.
This 「どれ」 is an interjection meaning "now", "well", "let's see", etc. It is most often used when checking on or taking a look at something. We also say 「どら」、「どれどれ」, etc. for the same purpose.
"Now, let me see the wound on your tummy. ...
According to this page, the attributive です connects to only ので and のに.
It's also possible to say ですこと and ですもの at the end of a sentence, but this こと/もの is usually categorized as a sentence-end particle rather than a ...
Both, kind of. It's an adverbial noun (noun that can behave like an adverb), so you can treat it like you would any other number + counter.
So your first sentence is almost correct (skip the に):
Alternatively, you can use の instead to use it attributively (but not な):
a) Although 因子を持つ子 can mean "the child who will have the factor", it usually means the same as 因子を持った子. Another verb of this kind is 含む.
b) 洗う服 is cloths you're going to wash, while 洗った服 is washed ones. So, 洗う服だけよけておいた means that you saved cloths you would wash and doesn't tell if you actually washed it or not. 洗った服… means you first washed cloths then put ...
絵を目立つ場所にかける (the original text)
However, from my point of view 絵を目立った場所にかける is natural... Because in Japanese, I often see 青目をしたお人形, 優れた人になりたい, 際立った特徴 and so on.
切る and 出会う (瞬間動詞)、 the difference between ル-form and タ-form is clearer
(that's more similar to the difference between 完了 and 未然)
for the status verb, how I can know when ...