I get the sense you are most interested in unusual linguistic features of Latin, which I'm not qualified to talk about.
It's also worth noting that 'why study Latin' is a well-addressed question in general (often aimed at the perspective of high school or college students choosing courses); Googling it will get you lots of results.
But besides this, a few ...
"Words neuter in Latin become masculine in Spanish"
This is generally correct!
In Latin, the most common type of masculine noun and the most common type of neuter noun look almost identical. They're only distinguishable in the nominative singular and the nominative/accusative plural.
In the branch of Romance that would eventually become Spanish, the ...
This is just to provide evidence for cōs-cōtis from classical poets:
saepe etiam duris errando in cotibus alas
(Vergilius, Georgica, 4.203)
(Horatius, Carmina 2.8.16)
nil tanti est. Ergo fungar vice cotis, acutum
(Horatius, Ars Poetica, 304)
All of these scan right if and only if cot- is read with a long vowel.
These are all the examples of ...
What interests you might not interest me; however, I have studied the languages you mention, among others, and might have some similar tendencies in what I find stimulating in language study.
I generally flit from language to language for a time and am currently restoring and extending my knowledge of Latin. What I find most interesting are the following ...
Rubrum is an adjective that agrees with vinum. The context of your phrase makes it clear they're both in the accusative (formally they could also be in the nominative or vocative), because vinum rubrum is the direct object of the sentence; "Velisne vinum rubrum?" translates to "Do you want red wine?".
There are languages that would use a ...