Futsal is governed internationally by the Futsal Laws of the Game, curated by IFAB, the same group that curates the Laws of the Game for Association Football (soccer). There are 17 Laws, although one of them (Law 11) simply states that there is no Offside. The basics of the game are identical to soccer, except in the dimensions of the court and markings, number of players and substitutions, the goal clearance, accumulated fouls, offside, the ball, and timing of the match. There are a few other differences, but they are mostly consequential to the other rule differences.
Futsal was created in 1930.
Marca Futsal was created in 2005.
Liga Futsal was created in 1996.
Futsal-Liiga was created in 1998.
Yes, boys can play futsal.
Nidaros Futsal was created in 2003.
There is no BMI requirement for futsal. However, futsal is a fast sport requiring speed and agility, and most futsal players are built much like soccer players are.
there isn't offside
Uzbekistan Futsal League was created in 1996.
Slovenian Futsal League was created in 1984.
Albanian Futsal Cup was created in 2011.