Would shortening World War I by a year prevent the USSR or World War II?
Short answerIt might prevent a Bolshevik takeover by improving Russia's position, but World War II still depends on Germany, the peace settlement, economics, treaties, and later political movements.
NotesA successful Gallipoli could reopen Black Sea supply routes and make Constantinople a conspicuous Russian prize. Food, supplies, and victory might buy the tsarist regime time or lead to a Menshevik rather than Bolshevik revolution. Whether World War II follows depends on Germany's peace terms, economic recovery, naval treaties, and the later rise of dictators. This is a plausible Russian divergence, with no confident basis for assuming that all later war disappears.