I think you missed this notice:
This section is dedicated to bugs & issues for the core sim (not mods or 3rd party content) – Utilize the voting system and only post if you do not see your bug listed. Please post one bug per topic and don’t forget to report bugs officially to [Zendesk]
There are several posts already in here on your issues.
Here is one.
(https://flightsimulator.zendesk.com/hc/enus).A320 climb performance
There are also lots of threads on it in other sections of the forum.
Regarding altitude restrictions, are you flying the mod, or the default?