>Join order can be forced by using outer join.
>Using of indexes can be disabled by changing of simple field usage to an expression.
>Preferences between ORDER and SORT plans (more commonly between "first row" and "all
>rows" strategies) can be changed by using FIRST/ROWS.
>Index statistics recalculation can be done in "a right moment"..

Thanks a lot for the information Dimitry.

One last question, does the optimizer actively learns and auto-improves from queries if we set the PLAN manually?

I had a slow query that I fiddled a bit the with PLAN, and the execution was faster.
I noticed that after a while, without needing to set the PLAN explicitly, the optimizer began using a different and faster PLAN then it was previously using.