1. He stopped smoking.

2. He quitted smoking.

Are both the same sentence?

Does #1 mean that he decided not to smoke again or mean that he turned the cigarette off after smoking for some time?

Both sentences mean the same thing. BUT the word would be "quit", not quitted. The three parts of the verb "to quit" are quit, quit, and quit.

There is no change with tense change.

The sentences mean that at one time he was a smoker and now he isn't.

1. "He stopped smoking." and 2. "He quit smoking." are similar sentences with a slight difference in nuance.

1. "He stopped smoking." This sentence implies that he made a decision or took action to no longer engage in the habit of smoking. It suggests that he has decided not to smoke again in the future.

2. "He quit smoking." This sentence also implies that he made a decision or took action to no longer smoke. It indicates that he has quit the habit of smoking and does not currently smoke.

Both sentences convey the same general idea of someone ceasing to smoke. The difference lies in the use of the verb "quit" in the second sentence, which emphasizes the act of giving up or breaking free from smoking. However, in practical usage, these two sentences are often used interchangeably, and the distinction in meaning may not be significant in everyday conversation.

Regarding your second question, the sentence "He stopped smoking" does not explicitly indicate whether he turned off a cigarette after smoking for some time. However, in this context, "stopped smoking" generally implies that he decided to quit the habit of smoking altogether.