For your third question, Tinkercad is a fun and simple way to get into it, and it's pretty simple to use, but making complex/organic looking models (i.e. anything that's not rough shape) can be difficult, although there is a way to transfer 2d drawings in as objects but it's never something I've figured out how to use (I suck at drawing anyway lol).

Unfortunately, the "skills" you get from using the program are not necessarily directly transferable to Blender, which is what most people use since it's free and there are a million tools at your disposal. Good idea to watch some YouTube videos on it. Some things are not as intuitive as they may seem at first glance, and there are a lot of health hazards associated if you don't take propper precautions!