Lottery conditions are determined by an agreement between the organizer of this event (operator) and a participant (natural person) - h. 2 Art. 1063 GK RF.
The contract is not in the direct understanding of the word, and by issuing a lottery ticket to a participant (in paper or electronic form).
The ticket must contain mandatory details, which are specified in Art. 12 ФЗ № 138 from 11 November 2003 of the year "About lotteries ..." (hereinafter - ФЗ № 138).
By the way, in FZ № 138 there is no such mention at all, as an "instant lottery". And it is said, that holding lotteries using information and telecommunication networks is not allowed (excluding international and all-Russian) - h. 4 Art. 6.1. ФЗ № 138.
Literally, this concept means the following - this is a lottery, in which information about a loss or win becomes available to the participant immediately after buying a ticket. An analogue of this concept is presented in ab. 4 h. 2 Art. 3 ФЗ № 138 (by law, the so-called sweep lottery).