I got to perform cleaning and replacing pads. Yes, the access is inconvenient, but I did not lower the muffler. And if you want to take down the whole assembly for renovation then you need to disassemble the rear wheel.
Yes, your screw is not original.
Check out my photos and decide if it's a problem? (I do not think there is a problem).
As for your screw head, it looks like Alan 6mm. Measure it before you buy.
For disassembly and cleaning of the caliper you need a lot of patience, knowledge... and the study costs money (the mistakes you make, the purchase of the appropriate professional literature, the purchase of tools ... etc.) ...
Because it's a matter of safety, maybe...feel free to contact a professional mechanic who will do that job for you.
Yes, your screw is not original.
Check out my photos and decide if it's a problem? (I do not think there is a problem).


As for your screw head, it looks like Alan 6mm. Measure it before you buy.
For disassembly and cleaning of the caliper you need a lot of patience, knowledge... and the study costs money (the mistakes you make, the purchase of the appropriate professional literature, the purchase of tools ... etc.) ...
Because it's a matter of safety, maybe...feel free to contact a professional mechanic who will do that job for you.