The first is not. 'That' is a subordinator there. The second is, but should be a non-defining relative clause.
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hanuman_2000I am not able to identify theAs I said, there are three and they are in sentences 1, 2, and 3 of your latest set. You wrote the relative clauses yourself, so it seems you should be able to find them.non-identifyingnon-defining relative clause.
hanuman_2000Could you please give some more tips on non-defining clauses?Defining relative clauses narrow down the set of references given by the noun to only those which are described in the relative clause that modifies that noun.
hanuman_2000Last week I bought a new computer, which I don't like now.Right. There is only one thing in the world that is the "new computer". No information you add to describe it will make it more clear which computer it is. So your clause which I don't like now is called "non-defining".