1 is a bit formal for spoken English (but some people like to speak formally, and some speaking occasions are formal). 2 is normal for any occasion - speaking, writing, formal, informal. However, the past tense of 'buy' is 'bought'.

Most important is that you need an article for ‘car’ : a/the/my etc.! Get/buy/acquire have different meanings. It’s not simply a question of formality. For example, using the rarer ‘acquire’ instead of ‘buy’ might lead to an inference that you got the car by some means other than buying it. ‘Get’ is the most precise if you don’t want to go into how the car came into your possession. It’s completely neutral. It tells the listener that getting the car is what is important to you. Omitting the article sounds so wrong, on the other hand, that a native speaker would immediately devalue everything that follows. It’s just not something that anyone who is fluent could ever say.

"Acquired" and "got" are both correct. Both words are fine in any context, but "got" is not a good choice. "Got" is the tool of laziness. It allows one to speak English without thinking. But it is not wrong. The past tense and past participle of "to buy" is "bought".

In general, written language tends to be more formal than spoken language—it evolves more slowly, so older and more formal expressions are still used even if they’ve almost disappeared colloquially. “Acquired” is a more formal version of “got”, and “purchased” is a more formal version of “bought”. I would most likely say “I got this car a long time ago”

1. Is formal English. 2. Informal English. Bought, not buyed, by the way. Well done.