1. Yes, but the benefit will be quite small. Oil filters tend to bypass briefly after a cold start. This is a transient event that tends to only last while the oiling system is building up pressure, so generally not longer than a couple of seconds. The thicker the oil, the longer the bypass event will occur.
The figure below shows oil pressures during engine cranking. The difference between curves 1 and 2 is the pressure drop across the filter. The pressure drop is very high for around 15 seconds of cranking, which might equate to ~2 seconds of idling. Once most of the oiling system is pressurized, it drops down to only 8% of engine oil pressure and the filter will no longer be bypassing.
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2. A higher pressure oil pump will increase the pressure drop across the filter, making bypassing more likely. This is why engines with high maximum oil pressures like Subarus specify filters with high bypass pressures.
3. No, as long as an appropriate filter is used, a filter should never bypass unless it's clogged. This is true even when the oil is cold and thick, since the oil pump will reduce flow enough to limit pressure drop across the filter. Even with the 10W-30 at -25°C in the figure above, the oil filter is not bypassing once the engine achieves stable oil pressure. The only exception to this is the transient bypassing as described in 1).
4. No, a thicker grade of oil will not increase the likelihood of bypassing in most conditions, for the reasons described in 3). Again, The exception to this is the transient bypassing as described in 1).
5. Bypassing lasts for a very short time after a cold start, but can happen continuously if the filter is clogged, or if an inappropriate filter is used.