[1] What is the best FREE software to make the 3d model?
Depends on you really - pick any you like and take a week to learn it (personally, I never seem to find what I need in blender, so I much preferred a leaner tool, had ac3d once and that worked better for me)
[2] what is the best FDM?
The one into which you put a lot of research to fill it with actual data. If you know aerodynamics, you'll find JSBSim quite comfortable, if you do not you'll likely produce rubbish and are better off using YaSim.
[3] How long would it take to make this?
A good plane - some 100 hours. Not including the time you learn the tools.
A great plane - easily 1000+ hours.
[4] Is there any coding involved with this?
Yes, but given the time it takes to create a great plane, the time you spend learning whatever tool you need is a minor correction - even if you sit a month learning how to code Nasal and canvas, it won't be that much overall.
But the advantage is - you can always start simple, create something flyable, keep working on it and improving it. And you'll always find people willing to help you out with specifics if you have something that needs to be improved - be it effects, AP design, avionics, liveries,... But you need something to show before you can recruit others to your cause