It's a common thing for there to be mistakes and misunderstandings. I've seen many errors in reference material that had been accepted as fact for 30 odd years. My advice, always, if you have time, check and verify.
To answer your questions.
1) It depends if they sell it as a round, or as component parts, and how they mark it up. In reality, the projectile should be marked up as OG-7 and the fin unit/propulsion charge assembly (the expulsion charge, its igniter charge, the fin stabilising unit and the tracer), as PG-7x, where the x is the model of assembly. The OG-7 is commonly supplied with the PG-7P, the fin unit/propulsion charge assembly used with the original RPG-7 anti-armour round, the PG-7V. This made up of the rocket-boosted PG-7 projectile (grenade) and the PG-7P fin unit/propulsion charge assembly.
2) What, the second image? That's a Bulgarian OG-7VMZ produced by VMZ (Vazovski Mashinostroitelni Zavodi). The image below is marked up.
3) As explained in 1), it's the markings for the fin unit/propulsion charge assembly. RPG-7 rounds use different assemblies depending on their aerodynamics and weight. Some Russian examples combinations below.
PG-7V = PG-7 projectile (grenade) + PG-7P fin unit/propulsion charge assembly
PG-7VM = PG-7M + PG-7PM
PG-7VS = PG-7S + PG-7PM
PG-7VS1 = PG-7S1 + PG-7PM
PG-7VL = PG-7L + PG-7PL
PG-7VR = PG-7R + PG-7PR
OG-7V = OG-7 + PG-7P
TBG-7V = TBG-7 + PG-7PR
TBG-7VL = TBG-7L + PG-7PR