Extended effect of the Heat Rock?

Question

I have some questions about the heat rock,

1. If a Pokemon who didn't activate the sun holds the Heat Rock, will it still take effect?

2. If the Pokemon with the Heat Rock not work anymore?

3. If the Pokemon is switched out, will the Heat Rock not work?

Answer 1

If the Pokémon holding this item creates harsh sunlight with the move Sunny Day or the Ability Drought, it lasts eight turns instead of five turns.

source
So that answers the first part. As for the other parts, once the sunny weather is activated, its duration is 8 turns
no matter what happens to the heat rock or the Pokemon holding it.