Reload .vimrc in Vim without restart

From the Vim man page:

-u {vimrc}

Use the commands in the file {vimrc} for initializations. All the other
initializations are skipped. Use this to edit a special kind of files.
It can also be used to skip all initializations by giving the name "NONE".
See ":help initialization" within vim for more details.

If you still want your ~/.vimrc to be processed, try this:

vim -u ~/.vimrc

Add the following line to ~/.bashrc (or your shell's equivalent file if not bash) to have the -u switch added automatically:

alias vim="vim -u ~/.vimrc"

You won't be able to add something to ~/.vimrc to prevent /etc/vimrc from being read, because the system file is processed before your user file (see ":help init", section 3, "Execute Ex commands, from environment variables and/or files").

:tab all

will open all the files in Vim's argument list in individual tabs. The argument list is initially set to the list of file names given on the command line when Vim is started. The list may be changed with the :args and related commands. See

:help :all
:help argument-list

Example:

:args *.c
:tab all

will open all the .c files in the current directory in individual tabs.