I want to make automatic restart of apache witgh cron. But what about everyghitng going in that moment - what will happen?

Will it finish last requests and jobs or instatly stop and then transactions will be rolled back?

Use reload:

sudo service apache reload

in practice Apache will perform a graceful restart, it is the same of running:

apachectl -k graceful

it means that will finish to serve the current requests before restarting.
For more information and options check: http://httpd.apache.org/docs/2.2/en/stopping.html

apachectl -k graceful

did not work.

apachectl -k graceful
httpd not running, trying to start
(13)Permission denied: make_sock: could not bind to address [::]:80
(13)Permission denied: make_sock: could not bind to address
no listening sockets available, shutting down
Unable to open logs
Action '-k graceful' failed.
The Apache error log may have more information.

But apache reload - did. Thanks