Of course you can have picnics on the grass! The umbrella shouldn't ruin the lawn, that may not be cool, but there are many big trees to sit under for shade, you won't even need a tent.
Picnic yes, not sure about umbrellas
I don't see that as a problem but they may have issues with umbrellas if it could potentially cause damage to lawn.
I did not see any written restrictions over there.
I think so.
Yes, you can.
I believe so, I am not sure on the umbrellas but I don't believe it would be a problem.
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