Programs used ? Can i use student licence programs ?

I use Wings3D for 90% of the models I upload here and it's free. Instead of using Substance Painter you could use Armour Paint for £20? I avoid using Blunder due its terrible export options (although that may have improved?) and terrible functionality and horrible UI lol

Selling your models is a great way to pay for the software you want, then you can use industry-standard stuff like Maya and SP. Good luck!

Blender can be used for commercial work without any restrictions. Regarding student licensing, there is no single answer. While many companies restrict usage of student licensed software to personal use and learning only, there are others that allows commercial use, so you need to look at it case by case. Specifically student versions of 3ds Max and Maya (Autodesk products) are restricted to personal use. You even get the warning if you try to open scene created with student version in regular version. In this case, no selling on stock market is allowed.

so can i use blender and sell my models on cgtrader ?

You can use student license to learn the program, but you are not allowed to use it commercially i.e. selling models made with it.
You can use blender for that though.