Sometimes I want to keep my question as it is and want clarification on it. So I don't want to allow edits on it. Sometimes it happens that some authors change the question in a way that changes the meaning of my question. How I can do this?
You can't. Once you've posted the question it isn't yours any more. It belongs to the community which can edit it, close it and delete it. There is no 'right' you are the only one allowed to edit and you can't stop users from editing.
That said, usually users are just helping you when they edit your question. Keeping mistakes in (generally in wording, never in code) is just a bad practice since it makes the question harder to read for future visitors.
Editors should not change the meaning of your post. If that happens, try to comment under your question and explain what you actually meant to write down and why.
If a user really defaces or harms your post, you can flag your question to let a moderator look into it, but never flag users who are actually helping you make the question better.
You seem to be asking "how can I prevent bad edits on my question?" not "how can I prevent all edits on my question?" The system is set up to make it simple to prevent bad edits.
First, edits from low-rep users must be approved by others. Second, you are notified of suggested edits and can also review and approve or reject them. Third, you can rollback any edit, or edit your post yourself to undo a change you don't like. Fourth, you can flag your post for a moderator and explain what has happened that you don't like.
Edits are explicitly not supposed to change meaning. When they do, it's typically because the post could be interpreted two ways, and the editor has guessed wrongly. For example, I have interpreted your question as "how can I prevent bad edits" while the other answerer has interpreted it the way you wrote the title, answering "you can't." Either of us might choose to edit your question to make it more clearly state our guess of what you meant. If we guess wrong, you shouldn't just undo our changes, you should also edit yourself to be more clear about your precise question. (This is something I learned as an author: when a copyeditor changes my meaning, it shows that the original sentence was unclear and must be rewritten. Rejecting the copyeditor's change is not enough.)
The whole SE system relies strongly on communal editing, and because of this both questions and answers are generally very high quality. (The voting system also works towards this goal.) Wanting to prevent all edits is in complete conflict with the goals of these sites. Yet there are plenty of mechanisms to prevent bad edits, which I hope you find reassuring.