I want to first try to sell my book without "distribution" option (and probably without ISBN).
Can I add distribution to my Lulu book later (say, after a year after publication)?
Yes, but you will need to revise the book to add the ISBN and distribution options. You will also be required to purchase a proof copy before you approve the book for distribution. Once you submit the book for distibution, it usually takes about 6 weeks for it to appear in online bookstores.