What are the SAAS solutions for those. support combined with the issue tracker?

Question

Helpdesk

Hello.
Tasks:
1) Answer users' questions (accept via mail request - a good bonus would be)
1.1) It is desirable that the user does not need to register to write a ticket.
2) If the question contains a description of the problem (bug, error, typos), then it should be possible to create an error and link to the task
3) If the question contains one of the existing problems, it should be possible to link it to it
4) It should be possible to divide tasks into public (which can be viewed by everyone) and private (which are only available to administrators/creator of the task)
5) It is desirable, but not necessarily a free / trial option.
Recommend some helpdesk + task tracker.
Thank you.

Answer 1

Stopped at helprace.com
Has everything except point 1.1