4 simple questions

I have 4 questions about wordpress and my blog (https://resumos.lusopt.info):

1) Why does appear characters like ? and ￡ instead of ? and á? And why this only happens in the section Recent Posts (Posts recentes)?

2) Why does pages appear in recent posts (posts recentes)?

3) Can I use my banner to link to the main page of the blog?

4) How can I customize my RSS page, doing things like put a logo on the right side?

Thanks!