Concluding that there was a peace agreement in place by early April of 2022 would be reading rather a bit much into what actually did occur around that time.
That such an idea ever did get into circulation was the result some bad reporting. An article was published in Foreign Affairs magazine, in which two respected commentators (Susan Hill and Angela Stent) stated "Russian and Ukranian negotiators appeared to have tentatively agreed on the outlines of a negotiated settlement."
Notice their use of such terms as "appeared" and "tentatively" - and even then only with reference to the mere outlines of a "negotiated settlement" (In other words, barely achieving any more than just establishing the agenda for any such discussions). Stent and Hill's report, while offering a glimmer of optimism, still strongly implied a fair measure of "ifs", "buts" and "maybes"! However, the way in which that Foreign Affairs article was subsequently reported has led to the circulation of much misinformation.
Any such ideas about a formal, negotiated settlement were fairly and squarely laid to rest as early as 7th April, 2022 (i.e. two days before Boris Johnson's visit to Kyiv). On that day, Russian Foreign Minister Sergei Lavrov announced that Moscow had in fact rejected the terms of the draft peace agreement which Ukraine had proposed. He claimed that it contained "unacceptable elements" that "deviated from proposals which negotiators from both sides had earlier agreed to".
Definitely, during the spring of 2022, no peace agreement was signed between Ukraine and the Russian Federation. Further, it was Russia who rejected the draft proposals submitted by the Ukraine, and this happened some two days before Johnson's visit.
(Hardly surprising when you think about it. The Russian negotiators were all low-level political figures without even any direct access to Vladimir Putin. They were certainly not invested with any plenipotentiary powers, and thus had no authority to sign anything).