You can eat anything at anytime but the earliest you would likely to get a hot main course served will be about 45 minutes after takeoff.
Two main courses might be possible but this depends on what is left after you have made your first choice and other customers have been canvassed for theirs.
Also bare in mind some customers might not order straight away and the crew will want to keep back some choices for later to allow this.
Salads come automatically in CW but you would be asked if you would like a salad in First and your choice of dressing.
The Captain announcement will be made 40 minutes prior to landing and that is around the latest time that we would serve any food and beverages as 20 minutes after this everything has to be cleared away for landing.
Hope this answers your questions?