  Isometry operations encode the quantum information of the input system to a
larger output system, while the corresponding decoding operation would be an
inverse operation of the encoding isometry operation. Given an encoding
operation as a black box from a $d$-dimensional system to a $D$-dimensional
system, we propose a universal protocol for isometry inversion that constructs
a decoder from multiple calls of the encoding operation. This is a
probabilistic but exact protocol whose success probability is independent of
$D$. For a qubit ($d=2$) encoded in $n$ qubits, our protocol achieves an
exponential improvement over any tomography-based or unitary-embedding method,
which cannot avoid $D$-dependence. We present a quantum operation that converts
multiple parallel calls of any given isometry operation to random parallelized
unitary operations, each of dimension $d$. Applied to our setup, it universally
compresses the encoded quantum information to a $D$-independent space, while
keeping the initial quantum information intact. This compressing operation is
combined with a unitary inversion protocol to complete the isometry inversion.
We also discover a fundamental difference between our isometry inversion
protocol and the known unitary inversion protocols by analyzing isometry
complex conjugation and isometry transposition. General protocols including
indefinite causal order are searched using semidefinite programming for any
improvement in the success probability over the parallel protocols. We find a
sequential "success-or-draw" protocol of universal isometry inversion for $d =
2$ and $D = 3$, thus whose success probability exponentially improves over
parallel protocols in the number of calls of the input isometry operation for
the said case.
