1) what file should I edit just to delete few social icons in "Social Share" or change order?

You can modify in this file. JoomlaFolder/administrator/components/com_easysocial/includes/sharing/sharing.php

https://monosnap.com/file/NSq7knc0qUt6VxQeqwxmVVi9POMfIM

2) is it any way to add more (Telegram, Viber, WhatsApp, Skype, ok.ru, etc) by editing file? I suppose it will bi diffucult to make system generate correct link (stream item's link for example).

You have to add the new functionality by yourself in order to support your personal needs :

1. You can refer our existing different social share from this folder how we do it JoomlaFolder/administrator/components/com_easysocial/includes/sharing/vendors/...

And this file JoomlaFolder/administrator/components/com_easysocial/includes/sharing/sharing.php

2. You probably need to understand how the other social chat like Telegram or WhatsApp sharing work, what kind of thing it required to add in order to share the link correctly with the content into Telegram and other social chat app.

3) if I'll edit file and replace all "icons" by code from this service https://yandex.ru/dev/share/ is will work, but system still will not detect current link correctly. So seems I need add new services one by one (use original code as example).

You can download my attached file and take a look what is the changes I have made for you, you can compare with the original file
JoomlaFolder/components/com_easysocial/themes/wireframe/sharing/dialog.php .


By the way, I am really sorry but unfortunately our support policy does not cover customizations

Thanks for understanding.