What version for Mocha for Windows 7 and above, should I buy if I want to go for IBM Mainframe access, AS400 access and telnet access?
All the versions are compatible with Windows 7. According to the official website, you have the possibility to download it for Windows XP, Vista, and 7. I believe you will need the Mocha Telnet version to be able to connect to UNIX/Linux servers. The tool is found on the same page.