Hi Samueel,
Good day! Based on my experience I found them on all posts in your website. I hope that helps.

You should be able to use it.

Yes

Hi Samueel,
For every relevant comment you give to another person's website by using the earn comments section, you receive 2 credits back, which is equal to 1 comment ask (it takes 2 credits to ask for feedback on your website). You should really read the website well, do your best to understand what they are writing about then give your honest opinions about the subject, your personal experiences with the subject if you have any, and ask relevant questions about the topic. Hope this helps! Good luck.

You can press on Website and site comments. There you can give two comments on people article and then request one comment back on your article, that way you can get comments on your posts which can help with building trust with your visitors and improving your search engines rankings.

But comments have to be good quality and be relevant to the post. It can't be something like a great post or well done. You should share your opinion about the post, ask questions and etc.
You can do the same with website feedback if you press on Website and Site Feedback. You have to give quality feedback for two people and request feedback for your site, which can help with making improvements to your site as you will get people to opinion about your site.

I use Sassy social share, it's a simple plugin that won't slow down your website. Jim

I prefer Social Media Feather, but there are plenty of options for you to choose from.

For me personally best one is Ultimate Social Media PLUS. Lot's of costumazation options, all social media, you can make a subscribe page or button, different cocial media icons and a lot more.