I am not able to read any of the photos due to their small size, so I will try to answer your questions without referring to what you are showing in them.
Increasing Flex VID (voltage) will increase temps. You want that to be as low as possible. If your system becomes unstable after lowering it, you have gone too far and need to bump it up a little bit. Try 10 or 15 and see how that works. This amount of flex should be fine for only 4.2-4.3GHz. Where you have seen me set this at 50 or higher, I am also increasing pri plane (watts) and that requires an unlocked BIOS. You also have a limitation with the MSR lock that can only be disabled with an unlocked BIOS. The MSR lock being enabled by default will be an impediment to overclocking. What will typically happen is the CPU core speeds will throttle (decrease) under load due to lack of power. This will happen regardless of temps. If the stock wattage is too low to support the overclock, the system may reach the overclock speeds, then drop to a lower speed as CPU load increases. If you leave the MSR lock enabled with an unlocked BIOS, your settings for pri plane will be ignored and you will still experience load-based throttling due to lack of power. Disabling MSR lock allows you to take control of the watts available to the CPU through increasing pri plane settings.
What you don't see from the screen shots is that my wicked benchmark runs with sky-high overclocks 4.7GHz+, 50+ flex and 1350 to 1375 on pri plane is using air conditioning to keep things cool. (Or, benching on the patio in freezing cold winter weather, LOL.) You should be able to run 4.2GHz without heating issues with low flex and a locked-down BIOS without complication unless you are in a warm environment. If you're working in ambient temps above 70°F, 4.2GHz is going to get warm. If you are seeing 90-95°C as a peak temp on random cores and that is not sustained on all cores under load, this is not a big issue. It's OK and normal to see random peaks that fluctuate among all of the cores. If they go that high and stay that high across all cores under sustained load, you will need to take steps to lower the temps to achieve the best performance.
The T-junction max (thermal shutdown trigger) for the Ivy Bridge CPU is 105°C. If your overclock speeds are staying under this threshold in a hotter than ideal work environment, you're OK in terms of having issues that demand to be rectified to avoid problems.
By overclocking your CPU you still have Turboboost if c-states is enabled. (If you have a stock/locked BIOS, then c-states is enabled because you cannot access the menu to disable it.) If your system idles to a lower speed, say 1.5, 2.0 or 2.5GHz and increases to 4.2GHz (or your max multiplier setting) under load, this is Turboboost in action. If you disable c-states (which I do) and your CPU runs full speed 24/7 Turboboost is effectively cancelled out because the CPU never drops to a low performance state. Turboboost becomes totally irrevelant and offers nothing of value with respect to performance in this scenario.
You can use ThrottleStop to control your multipliers without having to change them in the BIOS. You can set up profiles in ThrottleStop that allow you to have a variety of clock settings to use as you see fit. ThrottleStop includes a benchmark tool that lets you test the settings and observe the temps. ThrottleStop's 32M benchmark is very useful for checking stability and temps. For example, if you set your Flex VID at 10 and multipliers at 43x4 and the system hangs, ThrottleStop crashes, or your get a BSOD when running the benchmark, you know right away that 10 is too low for 43x4. You can drop to 42x4 and see if that works, or bump the Flex VID up to 12 or 15, then test again.
You can use HWiNFO64 to manually run the fans full blast or create profiles that control fan speeds based on temperatures, and this can be very helpful with overclocking. Running the fans faster at a lower temperatures helps prevent the CPU from getting as hot under heavy load.
When you set your multipliers at descending values (i.e. 43, 43, 42, 41, etc.) that means the CPU slows down as more cores are employed. Using the above example, your max core speed would be 4.3GHz with one or two cores in use, 4.2GHz when a third core is called upon and 4.1GHz when all four cores are being used. So, in that specific scenario, your Turboboost limit would be 4.3GHz. If you set them all equal (which I do using ThrottleStop) the CPU would run at the same maximum core speed regardless of how many cores are being taxed. Running all 4 cores at a maximum overclock multiplier value applies only to an XM CPU. With a QM CPU, maximum core speeds and SpeedStepping (individual core values) have a fused maximum value. Any values you set higher than the fused value with ThrottleStop will be ignored with a QM CPU. The core speed will no longer increase as soon as the maximum multiplier limit is reached.
I hope this helps. If you have other questions, feel free to post and send me a PM to alert me to your questions being posted.