Question 1: No spaces before or after the vertical bar
Question 2: Use the "sameas" flags when you have more than one Find A Grave memorial referenced on the same profile. Use "sameas=yes" for the FAG for the person profiled, use "sameas=no" if the FAG refers to someone other than the person being profiled. Use the "sameas=no" if the only FAG you have on the page is one which is not for the profiled person. You CAN use "sameas=yes" when the only FAG is for the person being profied, but it is absolutely not necessary. (In fact, I have been removing the "sameas=yes" from my own profiles as I encounter them.)
Question 3: Again, no space.
Here's an example not using "sameas":
Copy the citation at the bottom of the FAG page (click on the blue words which say "Source citation" to reveal the citation) Paste that citation. Delete the "https://www.findagrave.com :" Put {{ before the word "Find." Remove the space between "Find" and "A." Remove the space between "A" and "Grave." Type a vertical bar immediately after the word "Grave." Delete the words "Memorial no." including the spaces before and after those words. After the memorial number type }}.
The citation from FAG...
Find A Grave, database and images (https://www.findagrave.com : accessed 15 February 2020), memorial page for Tracy Kyle Everett (24 Apr 1894–12 Feb 1973), Find A Grave Memorial no. 137423178, citing Galatia Presbyterian Church, Fayetteville, Cumberland County, North Carolina, USA ; Maintained by NEVER EVER FORGET...... (contributor 48403481) .
...ends up looking like this in edit mode...
Find A Grave, database and images (accessed 14 July 2019), memorial page for Tracy Kyle Everett (24 Apr 1894–12 Feb 1973), {{FindAGrave|137423178}}, citing Galatia Presbyterian Church, Fayetteville, Cumberland County, North Carolina, USA ; Maintained by NEVER EVER FORGET...... (contributor 48403481) .
...and looks like this in the finished biography's sources list:
Find A Grave, database and images (accessed 14 July 2019), memorial page for Tracy Kyle Everett (24 Apr 1894–12 Feb 1973), Find A Grave: Memorial #137423178, citing Galatia Presbyterian Church, Fayetteville, Cumberland County, North Carolina, USA ; Maintained by NEVER EVER FORGET...... (contributor 48403481) .
It may seem a little complicated, but after you do it a few times, it becomes second nature, and provides a complete and correct citation for the FAG memorial.