Question: As stated from the questions title:

**What does 'beta' state of a SE site actually imply?**

Could someone elaborate, which restrictions or drawbacks we should expect from a *'beta'* SE site?  

I could have well been missing something, that's already been answered, or is an easy to find policies concept.

Answer: 
Beta sites aren't full sites. They're sites in a "trial" period, to see if they have the potential to become successful sites, or if interest in them wanes and the community dies out. From time to time, the site's community will be asked to [evaluate their site to ensure it is fulfilling its goal](https://meta.stackexchange.com/questions/161033/which-questions-need-community-evaluaton).

However, terms of functionality, beta sites behave like full sites, though with [reduced reputation requirements](https://meta.stackexchange.com/questions/58587/reputation-requirements-compared) for most of the tools, to make it easier for a brand new community to self-moderate.

The main difference between beta and full sites is the presentation. Beta sites all use the same generic theme and don't have a prominent link in the site footer (they're buried under "more").
Also, in addition to [Troyen's great answer](https://meta.stackexchange.com/a/239406/184589), another significant difference is that on Beta sites there are no moderator elections.

The moderators are instead hand-picked by the Community Managers from the pool of members that contribute with valuable content and demonstrate constant participation.