General qeustion about Hashtags

Hey guys!
- I wonder if there is any site/app that shows me how many people saw/liked/followed my post in a specific hashtag. (I only got Massplaner)
- How often can you be in the topsection of a hashtag? I guess only once?
- Is it smart to alternate Hashtag lists when posting twice a day? My first post is always in the topsection of my current hashtags. So i make the assumption that the secound post will be lost in the abyss of the hashtag.

I hope someone can help me!
Thanks guys!