1. -Do you need to automatically follow someone who follows you?
You can but you don't have to, If you like their account then go ahead.
2. -When you leave a comment and they reply back, do you need to reply back to that? I know it may depend on the comment, but in general. Does it depend on how engaged you want to be with them?
You should reply back even if it is a simple thank you but make sure you tag them. If someone leaves a comment like you know they want you to follow them, you don't have to respond.
3. Is it okay to post our products again if it's been some time or is it best to repost them with new hashtags?
Yes, you can, especially with new hashtags.
BethiesCards Queston
4. My question is: when we are doing these challenges and have to leave comments, should we also heart the item as well? I do if I like it, but wasn't sure if we should or not.
My fellow blogger Gigieats goes back and likes everyone, I don't but sometimes I do as a task.