Dungeons and Dragons

First off, you have an amazing community here, congratulations. It really touches me to see lemmy getting big enough to be of actual help, rendering that other platform unnecessary. Thanks for your input recently.

I was hoping you could help me clarify some other questions about the echo knight so I don't need to create an account on the Dnd Forums.

1. The echo can use the first part of the sentinel feat (says the FAQ on the forums) with it's reaction (reduce enemy movement to 0 with an attack of opportunity) - can it also benefit from the Shield Master (receive no damage on an successful dex-save)
2. can the echo be used for the protection-fighting style (use reaction to impose disadvantage on an attack directed at someone next to you)?
3. Can the ability to see through your echo avatar be used to create an echo at a spot your echo can see (that is still less than 1000' away from the knight)?

I hope that's all of them... Thank you so much in advance & keep on making social media social again :)