"Thought" is simply the past tense of "think" the complexities here are largely from the varying tenses of "buy" and "be" and how they interact with "think".
(1) She thinks that he bought a toy: This is her present opinion and it is not necessarily true.
Correct. This is a natural and common construction
(2) She think that he would buy a toy: This is her present opinion about the future and we don't know what will happen.
As written this is incorrect. It should be "She thinks that he would buy a toy" Indeed "She think" at the start of a sentence is an impossible form. With that correction, this is an incomplete conditional, more fully it would be "She thinks that he would buy a toy if...". That is, it is her opinion that he would buy a toy under certain circumstances. Those may be possible or impossible.f it had been her unconditional opinion about the future the sentence would be "She thinks that he will buy a toy"
(3) I thought that he bought a toy: This was my past opinion at that time and it has been proven that he did not.
Not quite. It was your past opinion. It may have been proved wrong, or rendered doubtful. Or you may still think that, but are recounting the process of your past thought processes and conclusions.
(4) I thought that he would buy a toy: This was my past opinion when he was walking around the shop. But after long time, he did not enter the shop.
That is one possible meaning, but it may also be the start of a conditional similar to that I discussed under (2). Context will help. Possible forms might be:
- (4A) I thought that he would buy a toy, but he did not.
- (4B) I thought that he would buy a toy if I gave him the money.
(5) I think that he would have bought a toy: He would have bought a toy
This is again part of a conditional form. The condition might have been given previously, or more usually subsequently. Possible forms:
- (5A) I regret that I didn't give him any money. I think that he would have bought a toy.
- (5B) I think that he would have bought a toy if he hadn't been late.
(6) She think that he would have bought a toy: He didn't and it is her opinion. And my opinion can be different.
Again this should be "thinks" not "think". This is very simialr to (2) except that the possible action of buying a toy is now in the past, and did not happen. It is also quite similar to (5). There must be a stated or implied condition under which he would have bought a toy, or at least under which she believes that he would have. She might be mistaken.
(7) **I thought that he would have bought a toy**: He did not buy. And I figured out that his ability and something that did not exist implied buying. But I figure out that only having very strong something that did not exist implied buying.
Again not quite. At the time, I thought that he would buy a toy if a condition (stated or implied, but usually stated) were fulfilled. I may have changed my view, or been provced incorrect, or I may have been proved incorrect, or the condition may not mhave been fulfilled.
Possible forms:
- (7A) I thought that he would have bought a toy if someone gave him money, and he did.
- (7B) I thought that he would have bought a toy if someone gave him money, but no one did.
- (7C) I thought that he would have bought a toy if someone gave him money, but he realized that he was late.
