What I mean by my question is this: Has the Septuagint and the Greek New Testament both been translated into Hebrew and put together in one volume?
These comments pertain only to the Septuagint portion of the question. OP elaborates in comments:
I was wondering if anyone has attempted to restore the original Hebrew text on which the LXX was based by back-translating the LXX into Hebrew.
The interest, then, is driven by a text-critical question and requests a reconstructed text.* In the modern era, there are two major projects of which I am aware that have attempted this in some measure:
Emauel Tov's Parallel Aligned Database -- most accessibly available via several major Bible software packages. The so-called "column b" contains the reconstructed text of interest to OP. From the author's introduction:
Column b contains a selection of retroverted readings, presumably found in the parent text of the LXX. At the same time, column b contains some remarks on differences between the LXX and MT in matters of translation technique.
Much of his technique is explained in an introductory monograph by the author.
Although far from a complete LXX back-translation, The Hebrew Bible: A Critical Edition (formerly known as Oxford Hebrew Bible) deserves mention here for anyone interested in the use of LXX for text criticism of the Hebrew Bible. This aim is a complete eclectic edition of the Hebrew Bible. When the editors deem that the "best" reading is found in a Greek text, this will be reconstructed in Hebrew. The project is explained in the prologue.
*By contrast, the Polyglot Bibles mentioned in another answer reproduce and align several received texts. In all cases of which I am aware, the Hebrew in such books is the Masoretic Text, even when it differs substantially from the LXX.
Translations of the NT (originally in Greek) into Hebrew abound. Modern versions are for instance available in the Biblical Society of Israel. Older versions are found online (e.g. here, and any other "polyglot bible"; see below).
The trouble is with translations of LXX, in particular with the translation to Hebrew of the texts that are unique to the LXX (i.e texts that are only in Greek; see this answer). It seems there is not a modern translation of these. In principle this could be achieved if there were a translation to Hebrew of a Catholic Bible, or of a Greek Orthodox Bible, both which include texts that are found only in Greek (see here). There seems however not to be such translation. For instance, the OT in all the Bibles sold by the Biblical Society of Israel linked above seem to be based on the Masoretic Text or Hebrew Bible, or on other Protestant bibles.
Another option however would be to look at polyglot bibles. The first one was developed by Origen, in the third century AD. From the XVI century onwards, several more were produced. I cannot tell whether any of these translated the LXX texts into Hebrew. You would need to search individually. On the negative side though, a 1901 bible called the Hexaglot Bible (because it comes in six languages, including Greek and Hebrew), only include books that were in the Masoretic Text (thus no LXX specific books). Another polyglot bible from 1863 in four languages, also does not contain LXX specific texts. Perhaps the most likely option was the polyglot bible called La Sainte Bible Polyglotte, published at the end of the XIX century, and which seems to be the only one published under "Catholic auspice". Unfortunately, as you can see by yourself (e.g. II Maccabees here), LXX texts not in the Hebrew Bible were left untranslated.