First of all, you need to understand that the issue of restrictive/non-restrictive clauses is irrelevant here. This is because your examples are ALL examples of restrictive clauses.
The relative clauses in your sentences define the noun in question and cannot be removed from the sentence. Simply adding a comma does not turn a restrictive clause into a non-restrictive one!
Non-restrictive clauses are independent from the core structure of the sentence. This means that they can be added or removed without affecting the meaning or altering the overall grammatical structure
of the sentence. For example:
"Iceland, which has some beautiful natural scenery, is an increasingly popular holiday destination."
If you remove the clause "which has some beautiful natural scenery", the structure and meaning of the sentence is unaffected. The sentence is saying "Iceland is an increasingly popular holiday destination" both with and without clause about the scenery. The non-restrictive clause merely adds extra information: it is not essential for either the grammar or the basic meaning of the sentence.
Now for your sentences:
1, 2 and 4 are fine. You can use either 'that' or 'which' in a defining relative clause, and you can also use 'who' to refer to a company. 3 is wrong because the comma should not be there.
7 and 8 are fine. They have the same meaning.
5 and 6 are wrong because they are not properly worded. Here are some suggested corrections:
5. I like to go to places where there is natural scenery.
6. I like to go to places where I can broaden my horizons.
Note that that 6 is a restrictive clause, so there should be no comma.
I hope that's clearer now.