The Locking of Questions

The first part has already been addressed in the other answers, heres the answer to the other half of your question:

can I delete a question once I’ve asked it?

No, you cant. I’ll give you the rundown about it… Questions only get deleted if they break the terms of use policy, which can be found in a link along the bottom of the page if you aren’t aware of the rules. The reason why people cant delete their questions is because someone may have that same question in the future and they will be able to use the search engine and find that question already asked and they will be able to see replies right away instead of having to wait for people to answer. What you can do though if you don’t want your question under your user name anymore is mark it as anonymous, heres how you do that: go to your profile, click ‘my questions” and on that page you have the option beside any of your questions to mark it as anonymous. This doesn’t get rid of the question completely, it gets sent to the ‘fau’ user.