Looks good Gracie.
Is that a gap under the board the level is setting On?
Check the bed and make sure there are no low spots. If there are, then just fill them in with thinset or medium bed mortar.

It's easier to install the backer board first before the mortar bed but not the law. The mortar bed helps anchor the board securely in place. Just make sure to attach the bottom section of board well to the studs and blocking.

I see quite a large gap on the shower floor from the right side to the drain.
As Harry said, fill it in so you have a 1/4" to the foot flat slope from the perimiter walls down to the drain.
Right now it doesn't appear that way.

I hope thats drypack around the drain and not just sand.

Gracie, please keep all new photos and questions regarding this one shower in one thread only. It would be less confusing that way.

I may try to see if I can merge your threads together.