Server Hosting would come with learning Web Development, not really much to learn there, just need to pay to have server space to host your final program etc...
As for sprite sheets, yes they can be made, but just depends on how deep you want to go as to how much work will be involved... since if you consider flash as just a white canvas and what you script in there is what determines what it will do...
Now, about 3D, normally thats a course on its own called something like 3D animation, as 3D can involve a lot of stuff from programming to how to build 3D models... so depending on which direction you want to go, and which you enjoy more you should choose to start with one or another first...
As for can you learn this in High School, i'm sure some HS can and do offer such learning programs although it really depends on your HS itself... otherwise, if you search online for tutorials on programs such as Auto Cad (3D model building program) you can get some idea of what you'll be dealing with...
But no matter which direction you go, be prepared to be nit-picking at a lot of code especially when something goes wrong, which at times will make you want to pull your hair out...
As for sprite sheets, yes they can be made, but just depends on how deep you want to go as to how much work will be involved... since if you consider flash as just a white canvas and what you script in there is what determines what it will do...
Now, about 3D, normally thats a course on its own called something like 3D animation, as 3D can involve a lot of stuff from programming to how to build 3D models... so depending on which direction you want to go, and which you enjoy more you should choose to start with one or another first...
As for can you learn this in High School, i'm sure some HS can and do offer such learning programs although it really depends on your HS itself... otherwise, if you search online for tutorials on programs such as Auto Cad (3D model building program) you can get some idea of what you'll be dealing with...
But no matter which direction you go, be prepared to be nit-picking at a lot of code especially when something goes wrong, which at times will make you want to pull your hair out...