1) Yes you can
2) No, but spend a lot of time reading up on wordpress codex (thats more or less your bible) and of course refernce through this site too, full of valuable information.
3) Everything is very easily added to wordpress via plugins, no need to go on steep learning curves
4) WordPress is probably the most simple of all to learn and very well documented.
5) of course WP is very flexible
6) There are thousand upon thousands of plugins (no need to re-invent the wheel) there is bound to be something that fits your requirements and as well as plugins there are also themes that have been designed specificaly for niche websites