GB UHD 4k - FlashMultiBoot - Howto ...

how to delete startup_2_3 and make clean partitions

/dev/mmcblk0p1: SEC_TYPE="msdos" UUID="3EC9-EF9C" TYPE="vfat" PARTLABEL="boot" PARTUUID="f280fd9b-351c-4fe5-bc1f-3cfa4fb8c07f"
/dev/mmcblk0p5: UUID="23aba023-235b-45cd-b04b-73be382e544c" TYPE="ext4" PARTLABEL="rootfs1" PARTUUID="0a0178a8-3e53-4ca6-939a-d9bd64fc866f"
/dev/mmcblk0p7: UUID="c026e034-1513-4d3e-b5d9-581cae6b08ba" TYPE="ext4" PARTLABEL="rootfs2" PARTUUID="31c5f89f-dde1-46a7-859c-6e1c06ec8665"
/dev/mmcblk0p9: UUID="599dec22-2f1b-4b3f-b988-6a4f832c64af" TYPE="ext4" PARTLABEL="rootfs3" PARTUUID="610f8264-3404-4de6-ab95-94a050e3c1b7"
/dev/mmcblk0p10: UUID="a49eac81-27d2-4f5e-b1a6-ac0e9695bf2e" TYPE="swap" PARTLABEL="swap" PARTUUID="f247ed3a-ab90-40d1-9ba4-6fee2444b06c"

and my multiboot selection startup_2 fails at boot sector %27 it crashed....how can I access startup_1 or startup_3?
and any way to see boot selector at startup without using openmultiboot?

Flash via WebIF or USB a clean image. That will automatically go to Startup_1. There you can flash images in Startup_2 and _3. You cannot cleanup everything? Why you should?