The version name always consists of several numbers and a letter, for example 0.2.1B.
The letter means the type of the release: “A” - alpha, “B” - beta.
“Alpha” versions are available to 20$+ patrons (or 25$ on itch). “Beta” version are available to 5$+ patrons (or 10$ on itch), but later they are released to public access with the next alpha release. Each build includes the content of all the previous ones. The average time between releases is usually 2-3 months.
Each major version is released in cycles, alpha for 20$+, then beta for 5$+, then alpha for 20$+ and beta with fixes and adjustments for public, then beta for 5$+, etc. 20$+ patrons get all the versions, 5$+ patrons get every second version, everyone else gets every third version. Each consequent version is built on top of the previous one and includes all previous content.
If the number of the version consists of three numbers, i.e. 0.2.1B, then the third number means that it's the hotfix for the original version in this release cycle (0.2B -> 0.2.1B -> 0.2.2B etc).
If you buy it here, even future ones (but only Beta versions)