It does cost to see Shoshone Falls as it is a city park. You can only park and walk over to the overlooks. I don't know what it costs but it is probably $5.
What Mary said
No, if crowded you might have to walk a bit.
They don't reserve spots for as anything there
There is no overnight camping at Shoshone Park or Duerkes Lake. There are several RV sites around the Twin Falls area.
Thanks! Your answer is awaiting moderation.