Yes. NBA players are allowed to compete in all FIBA 3x3 official competitions, including the Olympic tournament. This said, they need to comply with the eligibility rules.
FIBA expect Olympic rosters made of athletes playing regularly at the FIBA 3x3 World Tour, Challengers and the FIBA 3x3 Women’s League since these are the events which bring the highest amount of ranking points, an important eligibility criterion.
In theory yes though there is a risk of conflict in game times and schedule.
From November 2, 2018 (until November 1, 2019).
Actually no. It is in FIBA’s regulations that all FIBA 3x3 official national team competitions have the same number of men and women’s teams. They also play on the exact same court as testimony of FIBA’s willingness to promote women’s 3x3.
There are no limits to how many naturalized players teams can feature but all of them must have a valid passport dated before January 1, 2018.
The national team selection is a national basketball federation prerogative, subject to complying to the eligibility rules.
You can buy tickets on the official Tokyo 2020 website. For information, prices vary from 3,000 to 18,000 yens (i.e. €25 to €145).
The deadline for athlete nomination by the various national Olympic committees is on July 6, 2020.
The 3x3 event will be played at the beginning of the Olympic Games, from July 25 (2nd day of the Olympics) to July 29, with all the medal games happening on that day.