The daily spending limit is $1,000 per person, per day. This limit is set in law by FinCEN, the regulatory body for open loop prepaid access cards, and is not changeable.
For International Reloadable (INTL REL) cards, there is also a monthly spending limit of $4,000 per person, per month. This limit resets at midnight UTC on the first day of each month.
FinCEN understandably enforces significant civil (fines) and criminal (jail time) penalties for exceeding this limit.
Within that $1,000 daily spend limit, there is no limit on the number of transactions in a day.