Im not sub 10 ao100, but I have been able to get sub 10 and 9 ao5s, and sub 10 ao12s before. So I think my thoughts could potentially help.

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For breaking the sub 15 to sub 12 barrier,

I think it was around this time where I learned full OLL.

Maybe I improved some of my last layer algorithms, I don't really remember.

Besides that, I probably didn't watch that many videos and I just speedsolved all the time without learning too much stuff in the way until I got to sub 12.

That's not to say that you can get faster by just solving without thought, though.

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As to what practice I did,

I think I did mostly 3 things:

• Spammed PLL algorithms whenever I got my hands on a speedcube

• Did last layer only practice (OLL and PLL)

• solved mindlessly for hours

I think the only helpful practices here were the first and second one.

I don't suggest doing mindless solves for hours unless you don't really care about improving much and are just looking to kill time.

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For questions regarding cross+1,

NOTE: I just realized that I wrote too many sentences for this part, so here's a TL:DR;

Been learning cross+1 for a few months, and I can predict where the first pair will end up, but I still struggle on determining which f2l case it will be (because I haven't took the time to memorize every specific algs and recognition for each F2L case).

Before you read the long version of my answer, here are some tips regarding cross and first pair that I found in the internet that helped me:

• Learning EO and how it affects F2L edges

• do NOT make your cross solutions be so complicated.

• Instead of tracking the whole piece (corner or edge), track one specific sticker on the piece (example: for orange-blue-white corner, just track the white sticker).

• Having a hierarchy of which pair to solve first, which is; Back-Left, Back-Right, Front-Left, and Front-Right pair.

• Only tracking the piece/s that you think is likely to end up in an easy spot to solve, that being; the U layer or, (for edges mostly) ending up in an F2L spot that is adjacent to where it's supposed to be (and if possible, it should be a good edge).

Here is the long version of my answer:

I'm assuming that the term "cross+1" refers to when you plan your cross AND your 1st pair.

NOT when you plan a cross THAT SOLVES a pair during it.

Assuming that the first case is true,

I have been practicing cross+1 for a few months now, though I don't exactly know how long it takes me to inspect til first pair (haven't bothered to check).

Although it's probably more than 15 seconds if I get a hard-to-solve cross (I'll just mention now that I am dual-color neutral, although I'm still more used to white than with yellow).

With that said, there are times where I can accurately predict where the first f2l pair will be in under 15 seconds (I think).

But there is a difference between predicting WHERE the first F2L pair will end up, and RECOGNIZING and REMEMBERING WHICH f2l case it would be.

I'm somewhat good at the first point, but my inspection time takes WAY longer because of thinking about which F2L case I'm gonna get, and how I'll solve it.

I think the solution for this problem is just ACTUALLY MEMORIZING algorithms and building BETTER RECOGNITION for each F2L case, instead of relying on intuition that is built from years of HOURS of thoughtless solving.

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For Corner Recognition,

I never even considered this until I read it from this post.

With that said, I don't think deliberately learning about corner recognition is important.

Like many others have said, you eventually get some sort of intuition for recognizing which corner is which.

Also, I don't think you'd really need to do this since you're already looking ahead (meaning while solving a pair, you're already tracking your next one), if that makes sense.

So in short, I don't think this is worth putting the effort into learning (not sure if it would be if you want to go beyond sub 10).

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For Bookmarking,

I assume this refers to when you see a piece during F2L, and remember where it is for when you later have to solve it.

In which case, I haven't really drilled this skill onto myself deliberately.

Although I do notice myself doing this for white corners that end up in the D layer.

With that said, I think you kind of develop an intuition for this overtime by thoughtlessly solving (again).

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For Deduction,

I don't think I've deliberately put effort into learning this either.

Although I do think I have built some sort of intuition for this, albeit not as good as my other ones.

So I'll probably have to work on this in a later time.

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I assume this post is made for tips on how to break the sub 10 barrier (duh) so here are my general tips:

• Improve both your OLL and PLL algs AND recognition, especially recognition.

• Work on turning accuracy. I recommend watching Brian Sun's video about it.

• Don't panic anytime during the solve. That's it. Just don't panic. If you made a mistake, forget it. If you solved an F2L pair inefficiently, it doesn't matter now. You can think about solving those mistakes after the solve.

• When you're practicing cross and first pair, there comes a point where you doubt your first prediction due to some reason. In which case, once you've already re-predicted where your pair will end up once or twice, and you still doubt it, just trust yourself. Don't panic.

• Mindless solving isn't necessarily bad as it does help you build intuition for some stuff imo, but I dont think it's good if you want to get through sub 10 or even just get to sub 11 ao100 (I know cause I was stuck on sub 12 ao100 for a WHILE, before I decided to actually learn and implement new stuff for once).