Two Emacs challenges

[Leon]

Dear all,

I found two useful key bindings but they seems not obvious to achieve.

(1) Ctrl+Tab & Alt+Tab

Since most window managers have used Alt+Tab for switching windows,
Alt+Tab key bindings is useless in Emacs running in X. Is there
something I can set in ~/.emacs so that Alt+Tab will be remapped to
Ctrl+Tab? For example, if AUCTeX has bound <M-tab> to
TeX-complete-symbol, the function should be *automatically* bound to
<C-tab> when I enter LaTeX-mode.

(2) pairs

How to bind keys such as (, [, {, " etc to perform such function

When type once, it will insert a pair while twice insert itself for
example: `[' will insert `[]' and leave the cursor in the middle while
`[[' will insert `['?


Thank you all.
-- 
Leon