Predators/WMG

The soldier whose parachute didn't open, and who fell to his death, was Dutch from the first film!
Poor guy survived the events of the first movie with sheer badassery only to splat onto the ground due to faulty equipment.
 * If this is actually proved canon, I will laugh my ass off. And then feel horrible for laughing.

This is the Yautja's home planet!
just cause it'd be too badass not to see!

The idea of 'Seasons' isn't quite accurate.
They don't drop in one batch at a time, they continually drop in batches of animals to hunt. This is partially confirmed by Noland having been there for nearly forty years, describes ten seasons, yet the dead soldier at the beginning is only 'two weeks' dead (roughly) and they drop in a new batch right at the end. Perhaps they hunt for all of what amounts to a 'summer', then take the rest of the year off. So assuming a much bigger planet than ours, Noland's 'ten seasons' equating to about one every four Earth years instead becomes one a year accounting for an extra long year.

Those picked from Earth are replaced with biological duplicates.
Most of the cast could go missing without causing a stir, but the authorities would definitely notice an inmate vanishing from death row. The humans picked to be hunted would be lifted out and replaced with dead duplicates. Their autopsies would conclude death from bullet wounds, embolisms, or some other cause that would not be mysterious under the circumstances.

The dead guy, whose trap the group sprang, was killed by Nolan.
He probably pretended to be the guys friend before killing him for his stuff when the trap was complete.