They have the same meaning. There are two ways to contract "there is not": "there isn't" and "there's not". It's hard to say which is more common. This will depend on the overall structure of the sentence, the preference of the speaker, perhaps the dialect. My guess is that 'there isn't' is probably more common. I'd suggest you experiment by using both and choose the one that feels more natural for you - because both are correct. It is important to practise contracting because it will make you sound much more fluent and natural. Natives always contract in speech.

They mean the same thing. “There is not” is more formal or written language. “There isn’t” can still be written and is spoken more. “Isn’t” is a conjunction of “is” and “not”, you just push the two words together, drop the o and replace it with and apostrophe.

I agree with the other. Another option that is used more often depending on context is THERE'S NO. Examples: I can't take a shower; there's no hot water. The bar has to close, as there's no more beer.

Both are valid. The first one is more formal in my opinion

I agree with Vanessa. They are the same. Additional context and word choice in a sentence may lead one to use example over another. If in doubt - don't use the contractions.