At 50:1 you will need the engine to be jetted rich and to use an oil made specifically for an air cooled engine; designed to run at 50:1, without the engine being excessively laboured, especially at low speeds and rev's kept below 5,000
At 32:1 you can get away with any kind of 2-stroke engine oil so long as the engine is jetted slightly rich and not pushed too hard, i.e. revs kept below 5,000 and not laboured hard at low speeds.
At 25:1 you can get away with any kind of 2-stroke engine oil, at whatever revs you choose and at any bicycle speed in any temperature conditions, so long as the bike is jetted correctly.
At 16:1 you can get away with any kind of oil, even vegetable oil so long as the engine is not jetted lean. The downside is that it will carbon up the internals and exhaust and spark plug. If desperate to get home and out of 2-stroke oil, 16:1 will work with any oil you can find.
At 100:1 you will need the very best 2-stroke oil designed for an air cooled engine with everything working perfectly and the bike to be operated in a gentle manner without being pushed at all - also absolutely no air leaks; a carburettor that is jetted rich and a good fuel filter for any fuel restriction will lean out the mixture and it's bye, bye to the engine.