No u dont
Depends on who your friends are.
No
Technically yes. All OC parks/nature areas require a photo permit, however it is rarely enforced if you are not using an elaborate setup(costumes, props, lighting) just stay low profile and leave if asked.
If someone is being paid to take photos then yes a permit is needed. And as stated below you cannot set up an elaborate shoot. Anything with props needs a permit.
No, you can but they might shut you down if you set up with a bunch of equipment and a crew
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