selling shares

Q: I am trading in Indian share market. When I purchase a share it comes into my demat account (SHARE HOLDING ACCOUNT) after 3 days. Whereas when I sell the share it goes off from my demat account after 1 day. I know that it is forbidden to sell which is not in your possession. I have few questions in my mind.

1) As per the Indian stock market system I can purchase and sell at any time. But as per many Muslim scholars we should sell only when it comes into our possession. So I sell the shares after 3 days only though if I suffer losses. If I see losses then can I sell the shares before 3 days?

2) When the share are in my possession after 3 days then sometimes I want to sell it first and the buy it later on the same day. Is it a short sell? I want to clarify the mechanism for this scenario. I have 20 shares of xyz company in my account. I have sold it at higher amount and bought it at lesser amount on the same day. That means it should be deducted from my demat account and then again should be added to my account. As explained in point 1 it should take 3+1 day to complete the cycle. But this does not happen technically. Technically the shares remain my demat account. My question is- Is it permissible to do so? Or If I want to rebuy the shares then should I but it next day so that it goes from my demat account and then again comes into my account?

Q: If we interpret various Fataawa then it seems we can purchase shares and then sell them. But some people say that if you purchase the shares speculating that they will go up and sell within few minutes or after an hour or after some days then it is gambling. They say that the sole purpose of share buying should be the partnership of the company. If we are buying shares in anticipation of getting higher price afterwards, it is haraam. According to some muftis the sole purpose of buying the shares should be the partnership in the company and not trading. My question is can I buy the shares of a permissible company and then sell it when the value goes up?