Picnic and swimming allowed ?

Yes both allowed. It is a hike though so make sure ur coller has wheels lol

Picnicking/Grilling is not allowed at Hackers Falls. You can swim 50ft downstream of Hackers Falls, but not under or above the waterfall. Waterfalls, adjacent cliffs, and water within 50 feet upstream of waterfalls is closed to the public. https://www.nps.gov/dewa/learn/management/upload/DEWA-Compendium_May2020_FINAL_SJ.pdf

There are two ways to it, the one behind The Cliff Park Inn is much faster, it's only like 15 minutes

Swimming was allowed but you need to walk for about 30 - 40 minutes to get to the falls. Upon arrival to the parking they tell you picnic and grilling isn't allowed.