Yes. If someone you blocked can mention you by your username on Instagram. But this mention will not appear in your 'Activity' tab. If you block a person and then change your username, then that person will not be able to mention you unless he know your new username.
Quick Tip to Keep your Photos Safe
Making backups of your photos & videos is a chore you probably skip, but it really doesn't have to be hard. Here's an effortless way to backup photos - PicBackMan. PicBackMan is the easiest and simplest way to keep your photos safely backed up in one or more online accounts. Simply download PicBackMan (it's free!), register your account, connect to your online store and tell PicBackMan where your photos are - PicBackMan does the rest, automatically. It bulk uploads all photos and keeps looking for new ones and uploads those too. You don't have to ever touch it.