It's really simple: 1) insert a link to your telegram group / channel above 2) specify how many followers you need. 3) pay for your order.
Unfortunately, yes. Every promotion violates Telegram TOS. Though we don't aware of any such cases.
No. The only way to promote such groups / channels is to make them public for the duration of a promotion.
Yes! The only requirement is a channel being public.
Well we test every option that we have (that's why we don't have many). On the other hand other websites have lots of options, but barely some work.