All the criteria (a – f) must be met, according to the Geneva Convention, for a combatant to be described as a mercenary.
According to the GC III, a captured soldier must be treated as a lawful combatant and, therefore, as a protected person with prisoner-of-war status until facing a competent tribunal (GC III Art 5). That tribunal, using criteria in APGC77 or some equivalent domestic law, may decide that the soldier is a mercenary. At that juncture, the mercenary soldier becomes an unlawful combatant but still must be "treated with humanity and, in case of trial, shall not be deprived of the rights of fair and regular trial", being still covered by GC IV Art 5. The only possible exception to GC IV Art 5 is when he is a national of the authority imprisoning him, in which case he would not be a mercenary soldier as defined in APGC77 Art 47.d.
How sad you don't even bother to read something you use as a citation. Typical.