It's a Rubik's Cube you can only solve with your feet.
Is there any error?
Omitting "that" is permissible, but in good writing it is so much better to include it. "only" is technically in the wrong place, though licence in this regard is commonly allowed outside formal writing. It's a Rubik's Cube that you can solve only with your feet.
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Omitting "that" is permissible, but in good writing it is so much better to include it. "only" is technically in the wrong place, though licence in this regard is commonly allowed outside formal writing.
It's a Rubik's Cube that you can solve only with your feet.