Can the developer impose 10 per cent payment before showing documents related to registration, title, ownership & approvals while booking a flat?

You can only commit to such a condition because it includes your own risks. Ask the contractor if any conditions make the money refundable. That ensures you can get your money back without going through the formality of notice and lengthy bureaucratic formalities if you’re not happy with the validity of the paperwork or permits and you want not to purchase the property at all.