I believe the it is most common for a miscarriage to occur between the 6th and 13th weeks of pregnancy.
Vinegar will not harm a pregnancy.
A miscarriage can happen at anytime from implantation of the fertilized egg up until the 20th week, but most of them occur in the first 8 weeks. After the 20th week, it is called a stillborn birth instead of a miscarriage. A loss of pregnancy during the third trimester (after 28 weeks) is usually called a premature stillbirth and not a miscarriage.
Miscarriage
That's correct on all counts.
Possibly, if the pregnancy ended very early the hCG may have returned to pre-pregnancy levels before the miscarriage. It is more likely for the test to be negative a few days to a week after an early first trimester miscarriage.
If you have a miscarriage before week 22 there's not much they can do.
You have to see a doctor and have a surgical abortion.
Not necessarily. The hormones that make a pregnancy test read positive stay in your body for a little while after a miscarriage.
If you mean that shouting at the fetus or around the fetus or belly during the pregnancy can hurt it, the answer is no. And they can't hear until around week 20.
Normally it'll happen within the first trimester which is up to 12 weeks, after that the risk of a miscarriage decreases but it could still happen.
You can have a miscarriage at any time but rarely sex is the reason unless you have a very sensitive pregnancy and the doctor have told you to not have sex.