The M&P 15 will take a .750" gas block. This gas block should fit that rifle.
I would recommend emailing us at techsales@opticsplanet.com to help you further.
Most gas blocks will come with a roll pin. If one is still needed, we do have these:
https://www.opticsplanet.com/luth-ar-ar-gas-tube-roll-pin.html
Ideally you will want to dimple the barrel, pin the gas bock, or tighten the screws down and periodically check them. Locktite isn't as effective due to heat, nor is there a torque spec.
Yes, as long as your barrel has a .750 gas journal, this should fit.
No this does not come with the gas tube roll pin.
Yes, this should fit on a S&W M&P15 Sport II.
Yes, as long as your gas channel has a .750" diameter.
This gas block is a .750 diameter.