how many times can someone vote
I am not sure what your question is aimed at. Therefore, I'll elaborate a bit longer.
Our Poll Maker offers different types of votes. Most of them like allow you to vote once per option. For example, in a PollUnit with type photo contest it would be once per picture. If you would choose one of our rating types, you could set the scale. For example, for a star rating, you could specify the maximum number of stars that can be awarded per option.
With our voting type Dot-Voting you can determine how many votes each participant has in total, but also the number per option. For example, it would be possible to give each participant 10 votes, but only 2 may be awarded per option. Or 5 votes in total and one per option. You can also replace the default dot icon with hearts, stars or thumbs.
If your question is about how to make sure that each participant can vote only once or how to prevent fake voters please read the following article: Prevent multiple participation