These should be in separate threads, one per question:
But also have a look at the Advanced Rename section of the manual first, as those are both quite easy to do, especially using the macro mode where you can simply do the edit on the first file and see all the same changes applied to all the other files.
Tell us the issues (one per thread) or don't, but there's no point telling us you have a problem but without any information for us to actually help with it. Most crashes are caused by 3rd party shell extensions, and the FAQs have guides on how to track those down, which is a good place to start.