1. He tells me that she is happy.

=> He told me that she was happy.

2. He has told me that she was happy.
=> He told me that she had been happy.

3. He will tell me that she will be happy.
=> He told me that she would be happy.
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Q1: According to the change of the tense in the main clause, the tense in the subordinate clause changes as above? Is that right?

Q2: In #2, in the first sentence, is there no problem in using the verbs?

Q2:

The tenses in 1 and 3 are right.

In 2, the tenses are correct if you mean (in both sentences) that she is not happy anymore.

http://grammar.ccc.commnet.edu/grammar/verbs.htm#sequence

http://www.englishgrammar.org/sequence-tenses/

A1: Yes, you are correct. When the tense in the main clause changes, the tense in the subordinate clause also changes accordingly.

In the examples you provided:
- "He tells me that she is happy" changes to "He told me that she was happy."
- "He has told me that she was happy" changes to "He told me that she had been happy."
- "He will tell me that she will be happy" changes to "He told me that she would be happy."

A2: In #2, there is a slight problem with using the verbs. The first sentence could be rephrased to maintain consistency in tense. For example, instead of saying "He has told me that she was happy," you could say "He told me that she was happy." This maintains the past tense throughout the sentence.

A3: It seems like there might be a typo in your question. If you meant to ask something different, please provide more details, and I'll be happy to help.