@mary19c11, @deval_chloe,
Check your trust levels on your profile, and under badges:
!Viki Discussions
Basic
This badge is granted when you reach trust level 1. Thanks for sticking around and reading a few topics to learn what our community is about. New user restrictions have been lifted; you’ve been granted all essential community abilities, such as personal messaging, flagging, wiki editing, and the ability to post multiple images and links.
Member
This badge is granted when you reach trust level 2. Thanks for participating over a period of weeks to truly join our community. You can now send invitations from your user page or individual topics, create group personal messages, and have more likes per day
Regular
This badge is granted when you reach trust level 3. Thanks for being a regular part of our community over a period of months. You’re now one of the most active readers, and a reliable contributor that makes our community great. You can now recategorize and rename topics, take advantage of more powerful spam flags, access a private lounge area, and you’ll also get lots more likes per day.
If you’re not above Basic, there are plenty of restrictions. baepsae29 recently had to contact the help desk to get her member status manually updated. When she checked her trust level, she qualified for member, but the bot still had her at basic. 
Viki’s discussions uses the discourse’s trust levels, read up more here:
!Understanding Discourse Trust Levels
Yes, as noted by lutra, all three trust levels are restricted to three successive post, without another’s reply.