Thank you for waiting. We'll look at your concerns one-by-one.A. The planet be in the habitable zone
: Since this depends on how close the planet is to its star, this is definitely possible.B. Have Earth's mass, be geologically active and have water as well plant and animal life:
again, all possible. We'd have to assume that at no point did the planet become so hot that the water all evaporated, but that is within the realm of possibility, especially if the planet was at the far reaches of the habitable zone.
C. The star is old enough to have passed its active flaring age
: this is compatible with t he other information.D. The planet is not YET tidally locked. I assume the process of becoming tidally locked takes awhile (how long?)
: I'm assuming this is one of your biggest concerns, but it need not be. There is no set amount of time it takes for a planet to become tidally locked. It depends on its speed of rotation and revolution. When orbiting time equals rotational time, locking occurs. What causes the two times to become synchronized is the pull of gravity from the star. All you have to do is make sure your planet takes longer than its 36 hour day to orbit its star. You can read about this process in more detail on the Discovery site:http://news.discovery.com/earth/what-would-happen-if-our-planet-became-tidally-locked-130202.htm E. The planet has a large moon:
Not a problem. The moon's pull could even slow the tidal locking process, depending on its position.F. The planet has seasons----the length of the seasons is not important but I would like to know how long they would be:
That will depend on how long it takes to orbit its star.
If it took 100 days, each season would be 25 days long. If it took 400 days, each one would be 100 days. This is also based on the assumption that the planet is tilted on its axis (like earth).G. The days and nights are 36 hours each (plus or minus):
no difficulties here.H. The entire planet does not have to be inhabitable:
you're in charge of that.
If my world is possible, any comments on what it would be like living on its surface would be appreciated:
Much of this will be up to you, given all the parameters you have set out. If the planet was at the far reaches of the habitable zone, it would be cooler than earth. In the tropical areas, for example, the temperature might be stable at 60*F year round, instead of 80*F, as on earth. The poles would be extremely cold. In between, summers would be cool; winters frigid. Both days and nights would be long - 18 hours of each at the equator. There would be more ice on the surface than we have on earth. The long hours of daylight may result in faster plant growth during the growing season.
I hope this answers your questions. In summary, your world could possibly exist, maybe not extremely likely, but not impossible.