How to parse members of a VKontakte group and their groups?

Question

In contact with

Hello.
I don’t understand the contact API at all, but I need the following:
1) parse all members of my group
2) parse all groups that members of my group are members of
3) check in the Contacts section of all parsed groups for a link to the profile of any of those parsed from my group contacts
Purpose: to find group owners
Please help to implement each item. Or at least in words say what is needed to complete each item.
Willing to pay some...

Answer 1

one.

https://api.vk.com/method/groups.getMembers?group_id=1&count=1001&offset=0

Instead of group_id write the group id. Loop through changing offset. Gives out 1000 participants at a time.
2.

https://api.vk.com/method/groups.get?user_id=1&access_token=xxxxxxxxxxxxxxxxxxxxxxx

Instead of user_id - user id, works only with a token. The list of groups can be closed by the privacy settings, then no options. You can only check for membership in already known groups through groups.isMember or through the method from the first paragraph. isMember accepts up to 500 users.
3.

https://api.vk.com/method/groups.getById?group_id=1&fields=contacts

Instead of group_id .. Well, you understand.
The rest depends on the AP. VK API skips 3 requests per second and it seems not recommended to make many requests of the same type in a row. In general, longer intervals between requests are better.
Well, it’s not a fact that the owner or anyone in general is indicated in the contacts of the group.