Making a second jamaat in the masjid

Q: I have read a few times that men should not join the second and third jamaats in the Masjid. 

In the UK, many of the Masajid are very small, serving a large number or Muslims. However, in recent years they have introduced second and third jamaats to avoid people praying on the pavement which is used by everyone public. 

Is it still the case that instead of joining the second jamaat, men should pray alone in the Masjid?

One's supplier delivering directly to the customer without one taking possession

Q: I want to ask -  is drop shipping permissible or not? Let me explain the process: 

When a customer places an order, I contact the supplier to say that a customer has placed a specific order. The supplier then charges me the cost of that product from my bank account and then delivers it to the customer. So in that way, is it permissible or not?

Sharing the same hairbrush

Q: A family member keeps saying that he was told family members/friends, etc. should not share the same hairbrush as it creates envy and jealousy, he says a Moulana told him it's a hadith (he won't say which Moulana though). 

Now, as an Aalimah, I don't recall learning about this hadith but I could be wrong. Can you please help me out.