I hope you are not expecting too much from this contest because the prize is in a form of Free Spins and there is only 1 winner that you will choose randomly.
How about the winning amount from the free spins? Is it also coming with 35x wagering requirement or it is a free wager?
It is pretty clear that they have hired an inexperienced person as the promotional manager. They are only giving priority to the profit of the casino. The 'multiplier madness' contest will work as a win-win situation for the casino and lose-lose situation for the participants. The review contest is also going to be run in unprofessional way.
Checked the other promotion, and it seems that 35x wagering requirement is their standard rule for most of their promotion.
The other one I found is their lottery, a lottery where players earn ticket by wagering and the prizes also come with 35x wagering requirement.

The same rule also applied to the "Saturday Slot showdown" which is also a multiplier contest but with lower minimum bet ($0.25).
Come on Casinobet, while most other casinos do not have this rule, why do you apply it?
How can you be competitive with other casinos if you offer promotions which can be considered additional -EV for players?