I can help you with 1 and 3. Firstly, to determine if a plot is well-priced, search for similar either online (dealfish, nsoko and the various other property websites). based on a quick search, it seems underpriced. Also, visit the actual location and speak with people living nearby. If its significantly underpriced, antenna should go up.
To determine if its a genuine plot, ask for the title deed number and take yourself to Kajiado Lands office where you can do a search. It costs Ksh500. Finally, don't pay whole amount in one go and maybe use a lawyer-drawn agreement if you are still unsure.
Sehemu ndio nyumba