When to give first bath and how? And how to keep him clean untill then?

What are you trying to clean? Hard floors, fitted carpets or rugs?

 

Hard floor of tiles only as i have removed all the rugs and short carpets from the area.

 

Then hot water and soap should be fine - so long as the tiles aren't porous, you can clean them with anything that doesn't contain ammonia.

I just used dilute dettol on my floor tiles.