Think about that sentence.
The manacles prevent the character from attacking the orc.
The distance (because the character has insufficient movement) prevents the character from reaching the orc in one turn.
The suggestion spell prevents you from acting that way.
But above you are using "prevents you from taking that action" to really mean "doesn't offer an obvious explanation that I find sufficiently plausible." Nothing is actually preventing it.
So here's what's ironic: it's often the same people (including you, in this thread) who say that our way of playing is "pixel bitching" because we don't use fixed DCs, and we use the approach described by the player to adjudicate the outcome, who also think that the player needs to offer a sufficiently plausible explanation...as determined by the DM...to be allowed to know something.
How is one "mother may I?" and the other is not?