ME2 best possible ending

You can, if I remember correctly I got the IFF before I even started doing most of my side missions. I still lost Thane since I managed to fail his mission from having to leave the computer and forgetting to pause.

I'm not entirely sure about this though, it was after all some time since I played the game and I might have done the side-quests before I got the IFF, but as I said I'm pretty sure I didn't.

Hit the Omega 4 relay...

So you're saying there's no way I can finish all conversations with legion and tali?... since I can only do their loyalty missions before the abduction.

Correct, I always planned character acquisition/loyalty so that almost immediately after finishing Legion, the Normandy is attacked.

So I'll just do all loyalty and side missions (except Tali), then get Legion and do his and Tali's LQs, then get attacked and immediately go through O4 relay

Btw, does the order in which I do Tali's and Legion's quests matter?... I mean, I wanna know if there's any change if I bring Legion along for Tali's mission, after "freeing" the heretic geth... If the quarians react differently after learning I basically increased the main geth army. I also wanna know if Tali can still be proven innocent if I bring Legion for her quest.

And last question: Does the game allow me to complete all "just wanna talk about you" conversations with Legion and Tali, if I have an empty log after Collector attack? (seeing how you usually can't continue talking unless you've completed another main or side mission)

Not sure about bringing Legion to the Flotilla...

For talking/loyalty quests, you should be fine. From my experience you just have to have them on the Normandy and do one main/side mission while they're on board to unlock the conversation. Romancing, though, I don't know

Yes, I know that. I was asking wether the game lets you finish up all the conversation or not, since I wanna go straight through the relay and save all the crew. The problem is that, to achieve that, I wanna get all main and side quests BEFORE I get the IFF, after which I'll only be able to do 2 missions before the Collector attack, and those will be Legion's and Tali's LQs (wanna bring Legion along). I'm asking wether I'll be able to finish all the conversations without doing any more quests(since there arent any left) or if I'll be left with a "come back later" line, since you can't get personal conversations with the characters without completing their missions... and having Legion and Tali sort of "uncompleted" is kinda unsatisfying.

I had the same problem as you with my 3 playthrough as male.I recruited Legion before I left for Heastrom and after the attack on Normandy hit I wanted to complete Tali's mission for loyality and romance but I simply couldnt do that because when I reached Flotylla and click on "LAND" then suddenly EDI tells me that IFF is ready and the Collector attack begin.And I needed to complete her mission before "Suicide Mission" and that choice of mine maked all but my crew destroyed... When I played as female first I headed for Tali and I was able to complete every - side or main quest before leaving and keep everyone alive and the conversations shows up after you complete a mission not a moment before.The theory of "you can only do 2 missions before IFF ready" is rather a good one.I wasnt counting how many missions I was able to complete before attack but I think that it was number of 2.Also about Legion's loyality mission before Tali's... When I played as female I took Legion with me for Tali's mission but he wasnt loyal yet so I cant say how the quarians gonna react when you tell them that you increased or destroyed a number of Geth, but that is interesting thing indeed.If Im gonna play again (doubt it) than I will see to it.

Btw, does the game let you choose wether to install the IFF right away, or install it later, thus giving you time to do everything you need to do?... I just can't remember.

No I must submit to the game... but I've done all side quest before going to that Derelict Old Reaper.