1, The full form of HTTP2 is Hypertext Transfer Protocol Version 2

HTTP/2 (originally named HTTP/2.0) is a major revision of the HTTP network protocol used by the World Wide Web. It was derived from the earlier experimental SPDY protocol, originally developed by Google. HTTP/2 was developed by the HTTP Working Group (also called httpbis, where “bis” means “twice”) of the Internet Engineering Task Force (IETF). HTTP/2 is the first new version of HTTP since HTTP/1.1, which was standardized in RFC 2068 in 1997. The Working Group presented HTTP/2 to the Internet Engineering Steering Group (IESG) for consideration as a Proposed Standard in December 2014, and IESG approved it to publish as Proposed Standard on February 17, 2015 (and was updated in February 2020 in regard to TLS 1.3). The HTTP/2 specification was published as RFC 7540 on May 14, 2015

HTTP/2 ([HTTP2]) introduced a binary framing and multiplexing layer to improve latency without modifying the transport layer. However, because the parallel nature of HTTP/2’s multiplexing is not visible to TCP’s loss recovery mechanisms, a lost or reordered packet causes all active transactions to experience a stall regardless of whether that transaction was directly impacted by the lost packet

see also What does HTTP2 mean? What is the full form of HTTP2?

see also What does HTTP1 mean? What is the full form of HTTP1?

see also What does HTTP3 mean? What is the full form of HTTP3?