I have 2 sentences: A) I love this chair, which my father bought last year B) My city has a lot of beautiful places, which makes it a popular travel destination

Here are some questions. Can anyone answer?

1. Are the clauses starting with "which" in these 2 sentences relative clauses?
2. For sentence A, is it okay if I change ", which" to "that"? Because as I understand, the original sentence A uses nonrestrictive relative clause. If I use "that" instead of ", which", it will be restrictive clause, so it sounds odd to me because "this" seems kinda "restrictive" already?
3. For sentence B, if I change "which makes" to "making", is the clause "making it a ....." still a relative clause? Also, is the comma setting off the nonretrictive clause a part of it with the only purpose of separating the clauses?