Yes. It gets that extra leafy-mohawk look at terminal bud. You have preflowers at the nodes below, too. Single calyxes* form at each branch before anything else.
The plant was in flower before you can see it. It takes time for new anatomy to grow. Human eyes can't resolve cells dividing. Figure 5-10 days before you see preflowers
*Preflowers can form in vegetative phase of a photoperiod, if you keep it in vege phase long enough. But, this is very unlikely for autoflowers to occur given their time frame. You can safely assume it was in flower a week or so before you can see the preflowers of an auto. Depends on when we notice them.