GitLab.com is completely free, and has both unlimited private repositories and unlimited collaborators!

Except that it's unreliable, the website says so. Let me ask again, is there any plan without $390 onboarding provided by Gitlab that gives me following features:

1. Hosted Git. 2. Reliability.

There is none. I don't know why you seem to be trying to deny it. Your business obviously works with Enterprise. If I was a big corp, I'd be all over you. I'm not sure with Gitlab's compulsion with trying to make everyone happy. Even when they don't have a product that fit a nominal need in market (the 2 points above), they constantly try to insist that they do.

If you want reliable hosted Git right now consider https://githost.io/ (single tenant)

And we're working hard to make GitLab.com reliable, fast and free too.

Ignoring the name... are there any plans to make GitLab Mercurial capable? We still have Mercurial repositories and still sort of like Mercurial.

We'll not support Mercurial like we support Git, doing both would limit us to the features that are supported in both.

The difference is that Bitbucket offers unlimited private repos for free.

I edited my comment to point out that the same is the case with GitLab.com. (I should've been more specific)