...But we can see that only the 3rd scenario is happening right now i.e alts are following btc.
What's about the 1st and 2nd...
Recently, we have seen mostly one scenario where Bitcoin dump-altcoins also dump. And when Bitcoin pump-altcoins still dump. This is due to the fact that all the attention of investors is focused mainly on one coin - BTC. Therefore, regardless of the movement of BTC, altcoins continue to fall in price.