"Could Russia have won WW2 alone?"
No.
Let's time travel back to the exact moment Russia was in the greatest peril of being defeated, Operation Typhoon itself - the German attempt to take Moscow.. keeping in mind if that goes it is the centre of government and indeed Communism itself, centre of communication and transportation, the nerve centre of the military, etc; and that Stalin had thrown the last of all he had into the defence.
That very same year Lend Lease was arriving on Russia shores:
"The first shipments of tanks were dispatched in 1941, amounting to 487 Matilda tanks , Valentines and Tetrarchs from the UK and 182 M3A1 Stuart light tanks and M3 Lee medium tanks from the USA."
(A total of 22,800 armoured vehicles were supplied to the Red Army during the war, 20 per cent of the total number of armoured vehicles manufactured by Russia)
http://ww2-weapons.com/lend-lease-tanks-and-aircrafts/
A primary reason Operation Typhoon failed and Moscow was saved can be attributed to the British and American threat posed to the Japanese who preferred to garrison troops on supply on that front and in Manchruria than do battle against Russia - Stalin (through the Lucy spy ring) being made aware the Japanese had no plans of offensive action against Russia freed him to take troops from Siberia placing them in Moscow which proved crucial.
Had it not been for Allies period, Stalin would have nobody to ask for a Second Front from, which is exactly what Hitler wanted - to be free in the East to focus everything he had against Russia.
Even in intangable ways "Allies" played a part in Russia not succumbing, and that is why Allies are called Allies. There are countless stories of fresh Panzers mint from the factories being put on trains but never making it out of Germany to the Eastern Front, or any front for that matter being just victims of [western] Allies air supremacy and pilots happy to shoot up anything the moves.