Hi, Im currently a student ready to buy a catia software for my university classes and also for my future. And i have a few questions before i buy. 

1.  Currently my school uses Catia V5R21 software on all of its computers but i cannot find this version on your website to download and there was a promotion for the students right now and i really wanted to hop on this promotion. was wondering the multiple options is there a version where i can import projects from R21 to newer and also the opposite ; to make project on the newer version and open them at school with Catia V5R21. 
2. If all the new version are not compatible with the V5R21 is it possible to have a special request to get the V5R21 on my computer ? 
3. If i buy a version will it be possible to switch the version later in the future without charge ? or will i have to buy it again ? 
4. Catia is a very demanding program and i would love to integrate with my computer but im not sure if it will be able to run the program. If i pay and install the program but my computer is incapable of running or running smoothly the program can i just delete the current program on the existing computer and switch it over to a new computer without charge ? 
5. I currently have a Macbook Air, and was wondering if you guys have any method to help me run Catia on my macbook ( 1.6 GHz intel core I5, 4gb of Memory and intel HD graphics 6000)  or will i have/recommend to buy a new laptop ?

Sorry for the long list, thank you for you time i appreciate it !