Nothing about the number of events in ITF rule book, afaik
1. Open Competition / No Discrimination
Futures Tournaments are open to all male (please refer to Appendix A) tennis players based on merit and without discrimination subject only to the conditions herein set forth and provided, however, that minors under the age of fourteen (14) shall not be eligible for entry. For purposes of this Rule, the player’s age as of the first day of the tournament Main Draw shall be used.
ATP rule book:
A.Gender / Age Limitation
The ATP will use the age of a player on the first (1st) day of the qualifying competition. Male players age sixteen (16) or older are not limited in the number of tournaments they may enter. Players under the age of sixteen (16) are subject to the following entry restrictions in ATP World Tour or ATP Challenger Tour tournaments (includes entry as a wildcard):
1) Male players under the age of fourteen (14) shall not be eligible for entry into any ATP World Tour or ATP Challenger Tour tournament.
2) Male players aged fourteen (14) shall be eligible for entry into a maximum of eight (8) ATP World Tour or ATP Challenger Tour tournaments.
3) Male players aged fifteen (15) shall be eligible for entry into a maximum of twelve (12) ATP World Tour and ATP Challenger Tour tournaments.