You can return later, but you don't do it by going back to the entrance on the map. Just open the menu, go to DNA, then to Secret Locations, and choose to re-play whichever ones you need.
They are collecting the names of the ranks here:
http://forums.ubi.com/eve/forums/a/tpc/f/2361024388/m/5761082609/p/1
As for the symBols, nobody online seems to have compiled them yet. The top rank is the Abstergo symbol, that much is known. Under that, the best i can say is that the higher the rank, the fancier the symbol.
Lastly, as for calculating: there are three game modes. Free for all (wanted), Team (chest, manhunt), and Co-op (alliance). You have a seperate score for each mode.
This week's score is calculated by the best 3 scores this week in that game mode added together. Your total Templar Grade is the last four week's worth of these averaged out.
Example:
This week - 100, 200, 300 = 600
Last week - 100, 100, 100 = 300
No scores previous weeks.
Templar grade = (300+600) / 4 = 225
Yes, weeks you dont play count as 0 for that week.
There is also an Overall score that is basically the sum of all of your other Templar Grades.
P.S. Dont assume high ranks are good players, I've played with some pretty horrible players that are considered " Master"
Best Answer
OK so, from what I've gathered here and there, advanced equipment (and following evolved equipment) as well as color packs don't give any of the advantages I may have think of.
When you are given a target, the target picture shows the default equipment and color. Having another color/equipment selected can then confuse a little bit your pursuer.
Additionally, it seems players like customization! :)