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?

I have two 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 the two sentences above, relative clauses?
2. In sentence A, is it okay if I change, "which" to "that"? Because as I understand, sentence A uses nonrestrictive relative clause. If I use "that" instead of, "which", it will be a restrictive clause, so it sounds odd to me because "this" seems kinda "restrictive" already?
3. In 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 nonrestrictive clause a part of it with the only purpose of separating the clauses?