Upvote:2
For how long period do we need to book?
A booking should not be required. The permit should be granted even if you write "not yet decided" or the like. But the UK has been known to refuse EEA family permits improperly. If you want to play it safe, you can make a reservation for the duration of your intended stay.
If there is a temporary booking with pay at hotel option , would that create any issue with the UKVI. Does UKVI validate with the hotel?
It should not matter whether you have paid for the booking. The UK should not validate with the hotel. But they might do so, so above all you should not lie.
Any other option apart from Hotel? where temporary stay is available?
If you are visiting a friend or relative, you can list the friend or relative's home. But don't do that unless you actually plan th stay there.