the british have always fought against anyone creating a hegemony in europe
I would dispute that. Britain has always fought against any nation threatening its hegemony of the seas and trade. Or any nation where its European expansion would innevitably threaten the state.
Britain didn't go to land war against Napoleon's France until Napoleon blockaded the ports of Europe to trade with Britain.
Similarly in World War I, the main reason that Britain sided against the Germans was their naval expansionism. Germany was building a navy comparable to the Royal Navy with the obvious intention of siezing control of world trade.
The Suez Crisis is another great example.

The questions:
1 What if the allies had remained neutral after the invasion of Poland? Woud Germany have turned on Russia and if so what would be the result
They would have come across extremely cowardly after explicitly stating that Poland would be the last straw. Britain wouldn't have been able to tolerate this especially because the invasion of Poland restored Germany's control of its pre-WWI coast line giving them access to their old ship building territories. But since its a what-if to be humoured, Hitler probably would've consolidated for a few months and then launched an attack against France anyway, possibly after trying to get peace with Britain trading land for oil. Hitler needed the industrial regions in west Germany to be secure from attack, which with the modified borders from WWI and the new danger of air strikes would have been impossible. Without them he wouldn't have enough resources to pursue an invasion of anywhere. The delay would also have given the Germans time to assemble a more powerful navy and airforce than they actually had which would most likely have led to a succesful invasion of Britain.
2 What if the allies had declared war on Russia instead of Germany?
I assume America isn't being considered here. Britain, France and Germany would've won the war without a doubt. Even if Britain and France hadn't fired a bullet. The entire German airforce would have been available and the British could have supplied the Germans from the Middle East with all the oil they would need for a succesful invasion. If the British wanted to get involved to grab some land for themselves, they could've opened a second front by attacking the Soviet Union from the south from the Middle East or India. They could also have performed naval assaults too to open a third front.
At the end of the war, you'd have a big mess in Asia. It'd probably resemble colonial America by the end and when the Triple Alliance innevitably went to war (assuming no nukes) Russia could have tried to gain her independance, while the other nations battled each other into destruction.
3 What if the allies had declared war on both ?
Bad idea to go to war with two enemies who are at war with each other already. Better idea to secretly supply both sides so they destroy each other then go in and pick up the pieces.
4 What if the allies other than Russia of course had listened to Patton and attacked Russia after the defeat of Germany?
Then either the allies would have had to achieve a quick victory, which would have been unlikely given the length that their supply lines would become and the immense strain their infrastructure was already under or the American's would have had to used atomic bombs against Russia and central Europe. You'd then have had a huge power and geographic vacuum as these areas would be depopulated for generations to come. Britain and America would have been the two world superpowers once America had defeated Japan, as Britain would have been extremely unlikely to surrender much of their posessions without the game of pull and push being played on them by the US and the USSR.