In reverse order:
1. Strange stemming: the extra stems are for the English translation. Durand did the two-language version first and then just omitted the English text for the all-French version, leaving these vestigial remains behind. Very sloppy, Durand. Ravel had nothing to do with it.
http://petrucci.mus.auth.gr/imglnks/usi ... 5score.pdf
2. Measure 4: this is probably "experimental" impressionistic piano notation. They were trying a lot of "cool" things with notation, some good and some bad, just like composers today. Quarter rests are omitted for the upper parts as "obvious" given the meter and voice part that makes the rhythm absolutely clear. Simplifications like this are the bread and butter of keyboard notation in general, which tends to be creative given the desire of the best composers to keep the notation as simple as possible. Two more examples by Ravel:

- Ravel Sonatine1.jpg (125.24 KiB) Viewed 13832 times

- Ravel Sonatine2.jpg (70.43 KiB) Viewed 13832 times
3. measure 6: A 5:6 tuplet seems pretty tame to me, especially in this day and age! This certainly cannot be an error, since it took a lot of trouble to notate it this way. The quintuplet encourages a more free playing of the measure with a kind of folk-like hold on the D#.
The Russian version actually changes the meter from 3/4 to 2/4 to make the change from a 1/4 to an 1/8 note work! Unless the measure was revised this way by Ravel, it should be left as it stands.
I disagree with the idea that the greatest composers do "weird" things notationally. If something looks unusual in the work of such a composer, my first thought is: why this? Is there something deeper here that I am missing? Only when no rational reason can be found do I consider error and only reluctantly.
At some point, I hope to post examples of notational "oddities" that conflict with standard engraving practices but turn out to be little "works of genius" in themselves.
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