I assume you mean a 35.0 liter tank (10gal) and not a 90gal fish tank correct?
If you have a 10gal tank stocked that much already I wouldn't do a honey in there but if you REALLY want one in there and keep up with water changes (30% weekly) then putting ONE in there wouldn't be a big deal.
That keeps it as a centerpiece fish, minimizes fights, and less waste.
Well since its a 90 gal you could fit **** near as many as you want. 20-50.
Honeys are smaller and more friendly of the gouramis so they should work well together.
You could also instead get groups of other gouramis such as 10-15 pearl leeri's or 10-15 3-spot, 10-15 golden, or a combo of the those. If you get larger gourami's make sure you get enough to be a school or else youll have them fighting. Since you have guppy's I wouldnt get the larger gouramis.
I would also increase the number of Cory's you have. They love grouping and are much happier being around each other. Increase their numbers to 10 at least.
Good stocking-
15-20 honey
6-10 guppy
10 cory
That leaves room for more fish down the road if you want. Make sure you quarantine any new fish!
Thank you for letting me know1 month is plenty. A lot of people do 2-4 weeks. Depends on your comfort level and how the fish do in QT.