How does Ukrainian legislation differentiate volunteer categories, and what is a “volunteer participant in hostilities”?

Since 2014, volunteers are categorised into: (1) ATO/JFO volunteers later incorporated into official military formations, (2) ATO/JFO volunteers who were never incorporated, (3) fighters of Territorial Defence Units, and (4) members of volunteer formations of territorial communities. The status of Volunteer Participant in Hostilities applies to individuals who joined volunteer units between 2014–2017 and took direct part in combat during the ATO without being officially enlisted. To qualify, volunteers must have fought at least 30 days (continuous or cumulative) during the ATO in cooperation with official forces; documentation includes extracts from combat reports, certificates of cooperation and testimonies from at least three eyewitnesses (one being the unit commander).