There is no limit to the number of posts you can create in a day, albeit you probably won't pump out quality posts constantly and consistently.
In terms of the strict minimum time you have to wait before posting/PMing, that is simply calculated with the following:
waittime = 360;
if(activity >= 15)
waittime = (int)(90 - activity);
if(activity >= 60)
waittime=(int)(34.7586 - (0.0793103 * activity));
if(activity >= 100)
waittime = max((int)(14-(activity/50)), 4);
If you instead mean in terms of not spamming, there again is no minimum time. However, it is logical to assume that quality drops if the time between each post is less than 5 minutes (though there are exceptions).
So long as what you post isn't spam (or any other rule-breaking conduct), you can post as frequently as you'd like.
This information is the first time I have seen here, of that, if my account is old if I post with quality, I recover the activities?
Sample account for 3 months = 84 activities, correct?
If I do not post on this account for 3 months, can I recover?
or do I have to wait the next 14 days?
Only this information is missing to connect the dots!