Hi Deepak. Give me a call after the weekend and I'll see about organizing the use of a lift for you. I might even make an appearance and help you 😉
With regards to painting underside components, a good scrub with a wire brush, wipe with thinners then hammerite brushed on is as good as anything. Rattle can paint looks good but it's not really a durable finish. If you want to be really flashy, you can disassemble everything and get it powder coated. This is what I used to do when I worked in the restoration business. As @derik said above though, rust isn't really an issue here in UAE. It's just surface rust, it rarely eats through things. Back home in Ireland it's a real pain in the ass. Every winter they treat the roads with salt to get rid of the ice. Salt is a major catalyst for rust. Come spring time, it's 2 months flat out welding older cars patching sills and wheel arches.
As for rustproofing products, all I have ever used is Waxoyl. Bilt Hamber and Dinitrol also make alternative products but I have no experience of them. Pump it inside the chassis, sills and everywhere else. This is why vehicles have plastic rubber bungs in random places underneath, excluding the floor drains. Waxoyl is good but I don't think it would cope too well with an off-road vehicle here as the sand would scrub it off.
What they used to do in the olden days is use waste oil. Brush it on thick all over the bottom of the car and the oil repels the water. It's not particularly durable, it needs to be done 2-3 times a year but it works. I can remember my grandad doing it on his Austin 1800 when I was a kid.