is there any realization of temporary side chain?
for example for round of the game, when this chain only needed for players, who played this round in online game

What do u mean?

academy.binance.com start from there for blockchain basics

then move on to solidity

Have u even understood his question?

for round of game, ... is he referring to a mapping or a data storage, I understood it as that ... but with not much context given and confusion (on both sides) I thought it's best to start with the very basics to refer to him

if not he can refute my refer and provide more context

Like when there is a sidechain for dapp, but I don't want to keep it there is no need.
Like chain for communication level between parties, chain of signed proofs and other data, I don't need it after game round is completed, because even side-chain publishing is expensive when there is a lot of rounds and so on.

Maybe it's called just protocol off-chain communication.
But I believe there is also kind of standard, framework for making protocols like that:
1) connecting this parties
2) communication with messages
3) verification by each party
4) final results signed by each party -> then publishing signed result in blockchain/sidechain

So, I'm just looking how to make communication possible.
I don't really understand how usually it works or should work and what tools are used as good practices.

I don't think Blockchain is the right technology for your needs

Look at matrix.org

It may be overkill, bu lt sounds similar to what you want

why not? he's clearly speaking of gameFi, one of the cool use of blockchain tech

take a look to Fusionist, they building a full game on their blockchain and also a full ecosystem

Yeah but he's asking for a non persistent Blockchain, and do we even call that a Blockchain?

Have u read his requirements carefully?

i think you just need an off-chain script, similar to oracles who check, save and generate signed messages

i'm not into GameFi yet but i don't think a matchmaking system can be done on chain (it can but it's truly expensive), those needs to take the elaboration of data offline but keeping it "whole" with signed messages