If that's the lamp that came out, and you don't have the pin, then you're gonna need a new lamp holder. That bulb should have two of those pins on the bottom, not one. You might be able to prise it out from the holder with pliers (power off) but it's not looking good.
It doesn't help. You do not access the lamp from above, or by pulling the fitting out of the ceiling.
The bezel should detach by unscrewing it a quarter of a turn, as described above. In fact the bezel picture shows a couple of nodules that are the grips for your fingers so you can turn it.
If it won't turn then heat and time may have stuck the two halves together. You'll get there in the end.
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