This post aims to clarify most of the questions in this thread.
As Fexno indicated and as it was announced in the Achievement Dev Diary, many achievements do not apply retroactively and the calculation for them was started on the 7th of May.
There are certain retroactive achievements (like the ones about your level) that you should have gotten the rewards for, but also others (like time played) where the calculations started on the 7th of May.
Most of the achievements that the system can check in the information currently available on your account (like the information displayed) should be completed. However, I do not have a list of all these so please send a detailed ticket to support if you believe that an achievement was either not completed (although it should have been) or if you did not receive the reward for it.
I have already updated some of the bug reports related to and will continue to do so as I get more information.
On the 7th of May rewards from retroactive achievements should have been received. As previously announced, it is also possible that you completed more achievements while the Achievement System was implemented but not activated (after the 7th of May but previous to the 22nd of May maintenance). The rewards for these achievements were credited to your account directly (there was no mail about them).
Thank you, all, for your reports and your feedback and I will pass the information you provided on and continue to keep an eye on issues related to achievements.