customize according to mode

[Purnank]

Hello all,

I need one help.
On my system, c-indent-new-comment-line is mapped to M-j
But i want it to map c-indent-new-comment-line to "Return" when i am typing
a comment and
map "Return" to newline-and-comment when i am editing C++ file.

Also,
Sometimes there are tabs inserted in my file. and some time spaces.
If i use C-j (newline-and-comment) no tabs are inserted.
but if i use indent-region, align-entire, tabs get inserted.
Is this the default behaviour? How can i overcome it to insert spaces
explicitly.

How can i have Hungary Delete by default.

And,
Is it possible to delete trailing spaces? In some other editor i used
previously, it was possible to remove trailing spaces. The last inserted
space can be deleted from the same. Is is possible for Emacs also?

Is it possible to have bookmarks in emacs.
is it possible to insert comment block by default like,
/**
 *  <cursor is here>
 *
 * @author ....
 * @file .... some file.
 * @date ... TODAY.
 * (C) some company.
 *//* ****************************** */

Thanking You.
Purnank