Customization: flexible header, drop-down menu, social media & e-newsletter!

Hi!

My site is sufey.org and I have five questions:

1) How do you install a multiple-image header with a link to different pages (not posts)? Is it available on all themes, or would I need to code it?

Example: https://www.semperviva.com

2) How do I install a drop-down menu with a header that shows text when clicked?

Example: https://www.yyoga.ca/teachers-college/300-hour-teacher-training/ (Dates, Tuition, Sample Schedule, etc)

3) How do I add a e-newsletter signup as a thin horizontal header below my main one?

Example: https://www.marieforleo.com

4) How do I add custom social media icons within my header menu? (Little round circles instead of text)

5) How do I change my primary font size?

Thank you so much!! ??