You can send PM on forum.
What is a PM and how do I use it?

The test servers are only open for mass testing when a huge player base is needed to test an update. Though otherwise testing is help privately only for Testers to take part in, this is why you were prompted to give an invite code, as only official Testers have it. To apply you must speak fluent Russian among other things, and may fill out the application here.

You are welcome! :)

Please contact the Tech Support using this form.

You need to fill this form.

Please contact the Tech Support using this form.

Hi there, how can I help you?

How to change my password / email address?

Check these articles:

What to do if my account has been stolen?

How to protect your account against phishers, scammers, hackers.

Have a look at this: Invite Code for Test Server