Am i need to fill up the form twice if i want to participate in twitter and instagram or just make it become one ?

Just take where is more followers and add it.

Joined social media bounty campaign
Bitcointalk username: Ahasan
Bitcointalk profile: https://bitcointalk.org/index.php?action=profile;u=826395

Twitter profile link: https://www.twitter.com/cryptocoinbd

If my nickname is listed in the table, does this mean that I already participate in the campaign or do I need some confirmation?

done twitter and facebook task

we post 3-5 posts per week max, so it would be cool to like and share them all, at least 3.

Yep, and creating awesome posts or find awesome stories which are consider to be good to share.

Hi, I joined your facebook campaign. Can you please explain what are the requirements that we need to do. Do we just like and share your post or do we need to post something ourselves. Thank you.

Joined Facebook and Twitter bounty campaign.