Hi
So those 3 quests you mention all can take time (anywhere from 3-7 days in my experience) to show as complete.
For the LFG one, it's just a case of joining or creating an LFG on Xbox and taking part in it. And by taking part i simply mean being in the LFG party, either once you've invited interested parties or the LFG host invites you and you join - you don't actually have to play any particular game. You can also do this LFG mission with a 2nd account too (create the LFG, show interest using 2nd account, accept the request and invite and join party etc)
Gain a new follower - this is simply having someone add you as a friend (so they're a follower). You can do this with a 2nd account again or legit. You can use the same 2nd account to simply add yourself to complete it and then the next time the same quest comes up, simply remove your main account as a friend and add again
Make a new friendship - this is you adding people to your friends list and again can be done legit or with a 2nd account (keep adding and then removing each time a quest comes up)
Might also be worth checking out the ambassador subreddit (
https://www.reddit.com/r/XboxAmbassador/) where posts will be made of people sharing their gamertag, you can add these and send a 'GG' message and people will generally add you back
Some people i've added on there will also create LFG's which i get notifications for, a few people join and we all add each other as friends, send the GG messages and complete the LFG's whilst we're at it
Good luck and stick with it, soon you'll be getting up to the highest ranks each season without even thinking about it (i tend to get there around half way through a season now)