I won’t get my SIM at the airport.
I know the Megacom website, but it’s not in English. There are no prepaid cards on the site, only plans.
This here is the holder for my Megacom SIM card. Like everywhere, the card is sold in these plastic holders the size of a credit card:

Asian telecom operators (KZ, KG, TJ, UZ) work in terms of billing like the Russians. The concept of a long-term subscription doesn’t exist. But I think that’s also been the case in the EU, including France, for a long time. Basically, you can switch operators anytime.
The plan options, called "tariffs" in Russian (Тарифы) and "tarifter" in Kyrgyz (Тарифтер), are actually prepaid for a typical duration of one month, but sometimes less—and with Megacom, a week is possible.
If you don’t top up or set up automatic recharge via card or by deducting from your account balance, once the period expires, the card switches to emergency use only + the operator’s numbers for recharging and info.
The plans (tariffs) are a prepaid price for a month (or a week, in Megacom’s case), with the included data, call minutes, and SMS quantities for that price.
There’s a Megacom store in the airport on the ground floor, open 24/7.
When you buy one, the seller inserts and activates the card. ALWAYS. The buyer doesn’t have to do anything (except show their passport). That’s what Tatra explained.
Perju apparently bought a prepaid card in France—that is, a card with an initial plan but one you have to activate and validate yourself since it’s not sold in a telecom store. That’s the only difference. So you have to do what the seller normally does: enter the PINs included on the paper that comes with the card (this physically activates the SIM in your phone), then go to the operator’s website to provide your personal details (name, first name, ID document).