I'd like to participate and dont know where to start!
Are you talking about Ingress itself, different event types, or are you talking more about the Investigation side? Or all of the above? I notice you tagged things for both Ingress as a whole, Mission Day events, and Nemesis and Investigating so I want to be sure I know what you want info about. Also this might be a better topic for General.
Well although I would like to understand glyphs better, my question is particularly about the lore and current tesalations; is the event over? Can I still participate in the previous completed tesalaslations? Anything in should know that everyone knows in general? I find searching troublesome because there is so many topics and some not dated and I cannot find a timeline of the game events.
Alright well getting used to Glyphing, understanding the patterns, etc is best done by actually glyph hacking. You'll quickly get to know some of the patterns and the names. It's also good to start recognizing the names as well, not just go right to thinking of the glyphs as "bottom left triangle" and "big circle" etc. It's hard to break that habit once you get into it. Also, with the higher level portals, glyphing has four or five glyphs in each one and it will soon become apparent they form basic sentences.
As for the Tessellation event, it is completed and over. We still don't know what will happen with the in-person events like the Anomaly that was cancelled, but the event itself ended at the end of July. If you want to test yourself, the later Rounds (8+ i think) are all passcode-based. The Decode puzzles (the ones with pictures) will usually lead you to a portal somewhere in the world. Using the clues in the picture, you'd find the correct portal, add anything mentioned in the puzzle (some had an extra bit like the portal name plus a word) and enter that as a passcode in the Intel Map or the Scanner if you have an Android device. Now, these passcodes ARE FULLY REDEEMED but if you get the right passcode it will say "fully redeemed" so you know you got the right one. Otherwise it will say "invalid passcode".
As for Lore specifically, you'll have to look in numerous places, ask questions, and dig dig dig. One place you can look for the EARLY events is at www.nianticproject.com . After that, check out the Ingress YouTube channel and look at the playlists. There are many playlists given chapter numbers, and you can follow the development relatively closely.
Unfortunately, a lot of Lore and other information was lost when Google+ was shut down to the public, as that was where a lot of information had been stored. So it takes more digging.
If you'd like, there is a Lore group originally created by the NIA called Operation Essex that is on the Telegram App. We are open to anyone joining, all you need to do is ask! All you need to do is sign up on Telegram and send a message to a member, such as myself, and we'll be sure to get you into Essex. You're also welcome to send me any questions you have, help with decoding a Puzzle, anything! My name on Telegram is ArkFang, just like here. Just search for my IGN there and you're welcome to send me a message.