Everything just stated by the previous two people are guidelines. They are not true for every single case.
You CAN change distance snapping if it makes sense.
You CAN stack notes if it calls for it.
You CAN change the SV multiplier if it makes sense.
You CAN use CS higher than 3
Depending on the BPM of the map, 2/1, 1/1, 1/2, 1/4 can have entirely different meanings. For instance, for a 220BPM map on easy, instead of avoiding 1/1 beat overlaps, you might want to consider letting the 1/1 overlap but make sure the 2/1 beats do not overlap. Furthermore, 1/4 CAN be used in easy difficulties if the BPM is slow enough, or if you use a repeat slider that makes sense.
NONE of this is against the ranking criteria, but generally when you use things out of the meta when you aren't an experience mapper yet, you generally will do it in a way that isn't friendly to the user and/or plays badly, and mods will tell you to change it