It would be possible to do 4 days from Lake Ovan to the Caspian hinterland via Khashechal summit( 4120 m). However, if you are to walk from the lake itself you really need 5 days of trekking plus the day to get there and to get to Tehran ie 7 days in total. If you wish to walk it in 4 days ie 6 days in total then you need to leave out the summit.
Another option would be to start from Garmarood, where the ridge is lower and the summit you can do is off the path and is 3600m. There is a dirt road that you will have to cross 3 times on foot and there will be some cars passing from May until October but this will be a short stretch.
You may end either in Maran or in Yuj.
The main differences between the two are the crossing of a road which is absent from the first trek, and the fact that the first trek goes through some of the most pristine Hyrcanian forests terminating at 900m ASL but in option 2 the trek ends above the forest line at about 2200mASL and the rest is in a 4WD. There are pine forests on this latter option however and the view over the Alam Massif is quite spectacular.In option 3 below you will also trek through Hyrcanian forest and terminate at 1000m ASL.
Siyalan Summit the highest in Alamut at 4250m from Alamut Valley to Caspian hinterland in 3 days of trekking and 2 days from and to Tehran