It doesn't matter what shell you use. PL/SQL runs inside SQL*Plus, which is a separate program and has nothing to do with the shell.

If you mean for the purposes of practicing with the shell, any mainstream distribution will do. I have no idea what "Puppy Linux" is. For PL/SQL go to the Oracle website to see which Linux distributions they support, then go to the download site for that distribution and fetch a copy. For the purposes of learning shell, or PL/SQL, it doesn't matter which one you chose.

No. Bash is the default shell in Linux. It's a powerful shell, and you don't need to install it. If, for some reason, you'd prefer to use another shell, then you might have to install it. Whatever you do do not start off using the C-Shell.

There are plenty of resources both here (if you have specific difficulties) or on the internet (for general research).

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