Henry I. answered 12/14/21
Experienced, Patient Math and English teacher
1) Eliminate the second clause from consideration because it is a common declarative independent clause (he decided to become a novelist). The opening clause has a subordinating conjunction (while) followed by a present participle (studying). That's a marker of a participle clause.
2) If by inversion, you mean inversion of normal word order, it's certainly in this sentence. English most commonly has the following order: subject-verb-object (or other predicate material). The first clause of this sentence put back in the more common order would read, "He is not only a fast runner..." Note that the subject (he) and the verb (is) are inverted in the original.
Hope this helps!