Just choose if you prefer to do a photo contest or a giveaway. In the first one your users will profile tagging you and inserting the official hashtag of the contest.
In the second case, however, you will have to publish a post on get russian phone number online your Instagram profile and then extract the winners from the comments.
instagram-san-daniele-dop
Example of engagement rate on Instagram with giveaway
The more comments, the more engagement rate your Instagram account will increase!
Final clarifications.