- be able to play and get a S or above on hard/insane maps?
Hard: about 1 month I think (I could FC some of them since day one, but I couldn't get accuracy)
Insane: about 1 year I think (unless you count "Insanes" that are very easy)
- start playing with mods that increases difficulty?
Since day one for Easy/Normal difficulties. About 1 year for Hards, and about 1 year and half for some Insanes (mostly hidden only).
- be able to play maps like Lily - Scarlet Rose all the way to the end?
That particular map about 2 months ago (but I haven't really tried it before), maps with similar difficulty about 1 year and half (though with near a hundred, or dozens of retries at first, and gradually reducing the amount of tries needed)
- get ranked as first or top 50 on a map?
2 months I think (in this map
https://osu.ppy.sh/b/47886, the record was refreshed about a year ago by getting 1000 more on the spinner. Edit: the record was refreshed today, but the replay got glitched -> the replay shows I got 1,100 more than I really got in the play)
- be able to spin 400+ times a minute?
Since day one ~415rpm (when I started I had a grip that let me spin faster than now, when I want to spin fast I return to the old grip momentarily)
Playing Hidden I think comes naturally by playing a lot, when you are used to read maps you don't need the approach circles anymore most of the time.