I have read that some of the first TLD where registered back in 90s, including .cz, .pl and other. So domain .SU was. That was domains for national needs.
But who have rights to become a maintainer of national domain? How that procedure looks like?
I also read that .SU TLD was proposed by Finnish student. But how can a student register national domain that supposed represent country?
I couldn't find information about that on Google.
You can find all data on the IANA webpage at https://www.iana.org/domains/root/db or just query it with whois.
.CZ is listed as created on 1993-01-12 and .PL on 1990-07-30
You can go back with some in 1985 like .UK or .US.
.SU had a complicated life because, as a ccTLD it should not exist anymore as the country it represented does not exist anymore. However for non technical reason, it subsists. You can find some discussions there : https://www.icann.org/news/announcement-2-2006-12-05-en
But who have rights to become a maintainer of national domain?
This is a complicated question, and not a technical one nor a programming one.
In short, IANA uses the ISO list on country codes (with some exceptions, like .UK and .EU) and takes input from the relevant government. Now the problem is that some countries are not stable, and also change. So there are a lot of complicated cases. Some ccTLDs are also marketed as non ccTLDs (like .CO or .TV) because the government decided to give its management to some external companies, for some financial agreement.
"Mistakes" happen also, see for example https://medium.com/@Oskar456/stolen-sk-domain-717e070f6735
You can find more about the IANA process at https://www.iana.org/help/cctld-delegation
Each IANA decision to delegate a ccTLD to a country is associated with a "IANA report" listing the justifications. You can read them for whatever country you wish at https://www.iana.org/reports, like a recent one for .TD for example at https://www.iana.org/reports/2018/td-report-20180227.html
The core business is codified, before ICANN even existed in https://www.rfc-editor.org/rfc/rfc1591 IANA adheres to that, and you can find further documentation at https://www.iana.org/domains/root/help
For more details in general, I would recommend you to read my extensive reply to a related question about TLDs and wars: https://superuser.com/questions/1332236/what-happens-to-country-specific-tlds-in-a-war-involving-that-country/1332238#1332238