Can we launch multiple products using same account?

I guess there's a limit to launch products at the same time (not too sure about the limit though)

Yes, but at the same time I think you can launch just 2

Yes.

Yes, why not?

Yes

Absolutely! I'd say it's encouraged. If you've built up a following and reputation on this account, you'll get more traction for your future launches than if you would if you launched each product using a new account. Best of luck to you on your future launches!