Firstly, can I just say
to such a great day!
Do I let her sleep more then 2 hrs? Or do I wake her up?
I would wake her at 2 hrs and not let her sleep more than that because you want her to have a drive to sleep later on, if that makes sense. I am actually thinking that 2 hrs is too long for my LO as the other day she again skipped her catnap (and this time there was no one new around) and on this day she had 2x2 hr naps... she just didn't want to sleep anymore... that was an interesting evening lol!
Do I need to extend her naps if they are 1 hr 30 min or 1 hr 45 mins long?
No, you don't because not all babies will take 2 hr naps nor do they need to because 1hr30mins is restorative enough. For some babies (who's sleep cycle is only 40mins, 1hr20mins is enough and personally if my LO sleeps anymore than 45mins (be it just 1 hr), I do the happy dance, go to her, open the curtains and give her a big kiss for she has once again managed to transition through the dreaded 45 min mark hehehe
Do I need to increase A ( its 1 hr 50 min now)if S is 2 hrs . What if S is 1 hr 30 min?
I don't increase A time if S is 2hrs as opposed to 1.5hrs and I only
decrease A time if mine has slept less than 45mins as I find that mine can do the full A time even on a 45 min nap. If you are finding that she is doing well a the 1hr50 min mark, then leave that as her A time for now.
Do the A's need to be shorter before and after CN compared to A's in the morning and in the afternoon?
This is a good question! A times are generally shortest in the morning, before the 1st nap (not by much, maybe 15mins or so). With us, A times are anywhere between 2-2.15hrs, with the longest A time in the evening, before bedtime (no more than 2.5hrs)... and that's on just a 45min catnap. So I would say it depends on your LO and again it might be a matter of trial and error but the A time in the evening we have settled on (2.15-2.5 hrs, depending on how organised I am with dinner, etc...even after a CN) is fine with us and doesn't affect her ability to fall asleep or how well she sleeps at night. So it is quiet possible that your LO wasn't ready at 4:35 for the 3rd nap (CN) as she might need a little more A time (like mine, where A times increase a little as the day goes by).
Are you still doing the DF?