Hi! There are plenty of web-hosting companies in India. Which is best depends on you. Even here at the forum there are a few people (including me

) into domain registration and hosting. You can check out the bazaar section for the offers.
I haven't offered anything at bazaar section so if you need any information from me, please send a PM to me. Some members of this forum are using free hosting from me when I offerred it here some months ago.
There are plenty of people who can register domain names for you. But please ensure that you get complete control over it even if you have to pay a little more. Please note that whoever controls the domain name, controls the site!! Some of my clients have come to me after they have had problems with their earlier service providers. I had helped them recover their domain names

and have complete control over it.
No one can guarantee you 100% uptime. Most people guarantee a 99.9% uptime which is really reasonable. You must look for
cPanel hosting. cPanel is the best control panel to manage your hosting account and various parameters associated with it.
IMHO, Linux hosting is better than Windows because Linux is usually safer and more stable. Additionally, Linux hosting is cheaper than Windows hosting.