regards files and not its visibility protection

example that I want to do:
if I have this 3 files
MYSITE.com/index.php
MYSITE.com/one.php
MYSITE.com/two.php

I want that file two.php and file three.php aren't never accesible by url;
I think that is necessary some row in htaccess; not sure if is this
solution; or is necessary change file's CHMD ?

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other similar
MYSITE.com/index.php
MYSITE.com/A/B/one.php
MYSITE.com/A/C/X/other.php

is possible write in htaccess a code that if one write
MYSITE.com/A/B/one.php or MYSITE.com/A/C/X/other.php
is redirect always at index or see an error in the page?

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other:
for a directory which is the code for protect all the file excluse the
index files ?